While the redhead insisted there was no feud between Ulster girl Nadine and the rest of the group, she told Hello! that they have not heard from her since the autumn.
The band have taken a year off to pursue solo projects, with Nadine now based in Los Angeles.
Roberts said: “If I'm really honest, we haven't spoken to Nadine since we did the Coldplay gig at Wembley in September.
“I talked to the other girls about it on Monday and no, none of us have heard from her. But there's no feud.”
The time off has given the 24-year-old the chance to have “girlie chats” while visiting the other band members' houses — Nicola now lives in Weybridge, Surrey with boyfriend Charlie Fennell. She said: “You can just go round, curl up in your tracksuit on the couch and chill and talk about anything and everything.”
She added that the girls’ partners have to earn the approval of the other band members.
“We're like that film Meet the Fockers — we have a circle of trust and you have to earn your place in it. I wouldn't ever want to bring someone in just because I was smitten; lust can glaze your eyes over and you can make poor judgments.”
The full interview appears in Hello! magazine which is out now
An intimate relationship is coming to an end. This break will be sudden and disturbing. Resist the urge to patch things up. Right now, your differences are irreconcilable. You're better off going solo for a while. Rediscovering your independence will give you fresh confidence. Suddenly, it won't be so intimidating to go after the career you want. Applying for a job in the art or non-profit arena will be gratifying. You'll enjoy work aimed at making the world a better place.More