Contostavlos is mentoring the four acts in the groups category - 2 Shoes, Nu Vibe, The Risk and Rhythmix - and claimed that they have a shot despite the struggles faced by previous bands on the show.
"If there was ever a year it could happen," she said on The Xtra Factor. "I hope they've done enough and I can do enough for them that it could happen."
Contostavlos claimed that The Risk are "strong" as a foursome, rather than being focused on member Charlie Healy.
She also suggested that Rhythmix have a shot despite previous girl bands failing to do well on the show.
"I think this year it's different, I honestly do," she said. "No girl group before brought what they brought to the show. It's a completely different spin on things, and to all the females out there, I want you to support them. If any girl group can go far, they're the ones to do it."
She continued: "They're not against other girls, 'Don't you wish your girlfriend was hot like me'. It's all, 'We're girls, let's unite, let's stand up together, let's be strong'."
Contostavlos's fellow judge Gary Barlow also praised Rhythmix, saying: "They were superb tonight. Whenever I watched The X Factor in the past I've always hated the girl groups, but they were great tonight."
Four acts will leave the competition tonight as each judge picks one of their contestants to go home.
The X Factor results show will air at 8pm on ITV1.
> The X Factor Live Show 1: UK vs US: Live Blog
> X Factor Show One: You be the judge - Who sang best?
Watch our recent video interview with Rhythmix below: