She probably classes as overweight, but I'd say not obese. Yes, I think she has a beautiful face personally. I'm also a big believer of personality being more important than looks (but judging by the state of me most of my life I'd have to be). I don't know why she's getting hate for it though. X Factor is a talent show, and nobody can deny she has talent as a singer, which is what she wants to do.
Little Mix have proved that they can gel as a group, whatever they look like, and her weight just isn't an issue to her talent even though she might well weigh more than the average girl her age. Who needs to debate about whether she's fat or not? Yes, she has more meat on her bones than some other girls, but that's up to her to live with and her to deal with should she want to.. not up to anybody else to judge the way she lives her life or keeps her body.