Karen, 25, is the elder of the two and the blonde, pouting half of Alisha's Attic. She's also the confident one, the first to answer a question. Shellie, 14 months younger, is more intense, appears physically and emotionally frailer, yet on stage is the mad one.
Karen says even as schoolgirls they were always individuals and didn't run with the pack. "We were never cool", she says. "We were the ones who stood together on our own in the playground. The cool boys weren't interested in us. Never. There were girls who were part of the in-crowd while we had our own little gang - the weirdos. But I did fit in a bit better than Shel. She used to get into trouble, mainly with boys giving her hassle about something or other, like the colour of her hair. It would always be a different shade and that didn't go down very well in Dagenham".
Shellie chimes in: "There were a lot of people who thought I was strange. I was Miss Flamboyant, I never used to wear any shoes because I like the feeling of grass and puddles under my feet. I was just really individual. When people picked on me, Karen used to step in and help me out. She'd go (adopts bolshie tone), "Excuse me, do you know she's my little sister?' ".
Karen agrees: "I used to have arguments with kids at school who were always picking on Shel. And now, if someone is having a go at either of us, that sets me off. I have no qualms about giving them what for. I'm quite sensitive but I can also be tough, and I won't let anyone take advantage of us. Ever. I'm not frightened of anybody".
"Not like me", says Shellie. "I'm frightened of everyone. I can't handle conflict. I can't be aggressive with people. I'd rather be at home, crying". Shellie has suffered from obsessive compulsive disorder (OCD) for years. "I was born with strange ways", she says with a shrug. "I had an imaginary friend when I was about four and that carried on until I was 13. My OCD isn't quite as bad as it used to be, but I'm still very controlled by it. I feel as though I have to do certain rituals, or it'll be unlucky and something really bad will happen to me".
At first, Shellie's compulsion was cleanliness. "I thought everybody was dirty", she explains. "I used to make my hands bleed by washing them so often, and I never used to touch anything. I'd pull my sleeve over my hands before I could even flick a light switch. I don't do that anymore, but I have to be really in control otherwise I freak out. Before I leave the flat I have to knock on the front door in the shape of a cross. If I can't I totally freak out and start crying. Sometimes I think I can be really brave and walk away without doing it, but I always run back. The fear takes over".
Karen jumps in supportively. "I think it's really good you can talk about this", she tells her sister. "You know, a lot of people suffer from it but are too embarrassed to say anything, and that's wrong". She pauses, laughing, and adds, "It does drive me insane, though!"
The girls come from an arty background, with a singer-turned-author father and a mother who was once a ballet dancer. When they left home at 16 they moved into council flats down the road from each other, started writing songs they recorded on makeshift equipment in a friend's attic, and began gigging in pubs and clubs. And like hundreds of other wannabe pop stars, they sent their demo tape to record companies along with hopeful letters.
"We must have had at least 20 rejections", recalls Shellie. "Yeah", adds Karen, "they'd tell us they liked the songs but not us. Or sometimes, when we sent a photo, they called to say they didn't like the tape but did we want to go out for dinner? We'd tell them to naff off. There were a lot of people who didn't believe in us, so our success is a kick up the backside for them. Even now, some men in the music business can't accept you have a brain and wear a bra. It's an explosive combination".
Their big break came when Mercury Records heard a demo and immediately gave them contracts. The girls signed up over a celebratory meal with managing director Howard Berman. "It was the most embarrassing moment of my life", remembers Karen. "I wave my arms about a lot when I talk, and I knocked a bottle of red wine over his suit. He laughed, but I knew it was because he felt he had to. I nearly cried. Shel was shooting me poisonous looks and I really thought I'd blown it".
Now the sisters are so well-known they're often stopped in the street for autographs. So, how does all that lovely fame feel? "Well", says Shellie, "we work more and we travel a lot, but we still go home and clean out the cat shit".
They've also kept their close mates, and Karen has a boyfriend she's been going out with since they met at school eight years ago. "He's really independent", she says. "If I can't phone him for a while, he understands. I prefer male company. Some women can be dead bitchy and talk about you behind your back. I like sensitive men who can chat for ever. I talk about all sorts of things with my male friends. And they all know everything about me".
Fame has also meant the girls have ridden on the back of Michael Hutchence's motorbike in the south of France, met East 17 ("So lovely!'), and Reef ("Beautiful') but, says Karen, "I see more people I fancy in the street than I do big pop stars or actors".
Anyway, she's the faithful sort, and plans to have a big wedding, children, a house in Oxford and a couple of springer spaniels. Meanwhile, Shellie's not sure if she wants to marry at all. Recently single, she confesses: "I can't remember the last time anyone asked me out. I said the most awful thing the other day. I was sitting in a bar and this bloke said "I thought you were going home?' and I said "I was, but I stayed to look at your face one more time'. As soon as I said it I was cringing. I was like "Oh no!' You know you've made the most stupidest impression".
Karen looks horrified. "I'm not very forward with men", she says. "I stare at them. That can work wonders, you know - keep quiet and let them approach you".
So, what would Shellie's ideal man look like? "I like older men", she says. And, lads, it positively helps if you're ugly. "I fancy blokes like Al Pacino and Prince", she says enthusiastically. "In fact, I like anyone who has an odd feature such as a big nose or a pock-marked face. I don't like obvious good looks that slap you in the face. My last boyfriend was very weird looking, he had tattoos everywhere. Lovely bloke, though".
Onstage, the girls come across as wickedly funny Essex vixens. "Why are you wearing sunglasses when it's dead dark in here?" Karen heckled a pleased-with-himself bloke in the crowd at a recent gig. "Come on, take "em off. Are you gorgeous under them or what? Oh Shel! Look, he is". "Cor, yeah! Lovely!" added Shellie enthusiastically as their blushing victim sloped off to the safety of the bar.
"We have a riot on tour" laughs Karen. "It's just us and the boys in the band - all that testosterone!" But it's a drug-free riot. "I support the legalisation of cannabis", she says, "but I've never smoked it. We do get offered stuff, you know, coke and dope mainly. But that's not because we're in a band - drugs were available at our school in Barking. We have friends who are addicts and others who are recovering, so we know it can be pretty rough. We chose not to get into that scene. It frightens me to think what a tab of E can do. We're not preaching, though. People have their own choices - and mistakes - to make".
With the sex and drugs under control, Karen and Shellie are now concentrating on rock'n'roll. With some powerful live performances behind them and a new album on the way, they're now off to the States. "Breaking America is my biggest ambition" Shellie smiles. "Really?" says Karen. "I want to swim with dolphins". She pauses. "And sell out Wembley".