Frankly from the way you are massively projecting on to your daughter on this thread, and making a practical problem for her a psychodrama about you, I wouldn't be surprised if you have given her some serious issues around food and weight.
Maybe give way to her dad on this one, as you don't seem able to come at this as a strong supportive parent - your own insecurities and issues are too triggered.
Tell him that he needs to broach the subject with her in a gentle, loving way, and encourage her to buy clothes that show how beautiful she is, rather than emphasising the things she doesn't like.
More to the point, maybe he can encourage her to join him in loving and respecting her body more - take her to the gym with him, show her how to use weights, get into a bit of friendly competition about PBs etc, ask her to cook and eat with him. Try and be a more active role model and support for her.
Please don't push your issues onto your daughter. You are assuming she feels the same way you do about her weight gain, which she may well do, but it won't help for her to know how much shame and self-hate you feel around your own weight issues - all that tells her is shame and self-hate is how she should feel too.
There is no shame in weight gain, all bodies are equally worthy. But people who love themselves look after their bodies. Let her love herself, at any size. Best thing you can do, until you have your own self esteem issues under control, is to back off the issue completely and give this one to dad.