It was mentioned before that she lost more than 10lbs or something?, still, I don't think she looked fat with a little more and I def don't think she is too skinny now.
She posted another picture with her stomach showing a day before the picture from the opening post and her ribs aren't prominent in that picture at all. So that's is why I (and many other people) think she's been sucking in her stomach.
She's not too skinny and she's not unhealthy, but sucking in her stomach does make her appear that way and instead of just admitting that she's sucking in her stomach she claims that her ribs are always prominent even when she had more flesh on her bones. When she's been posting so many pictures, it is easy to see that this is a lie.
She never got any comments on her weight before and she probably wouldn't have now is she hadn't sucked in her stomach.
Just don't chew someone out, don't lie and don't scream bloody murder because you're not willing to admit you made a mistake.