How to help daughter with weight issues?

I admit, I am NOT at a healthy weight, 107lbs over a not healthy weight. But I’m very concerned for my daughter.

She’s 12 and 5’6”. She’s taken after my side of the family so she has a bulky frame. In May 2010 she weighed 120lbs. She just weighed herself again just last week and she is 198lbs. She is absolutely devastated! She has no clue how she gained 70lbs in less than a year. And yes we weighed again to check. She doesn’t think she’s beautiful, which trust me she is, and she wears clothes in a way to hide herself. I asked her if she stress eats, she doesn’t know, I asked her if she gets enough water, she doesn’t keep track. She just said she’s constantly hungry.

I know that with me being obese and having a severely low self esteem doesn’t help me with trying to help her. How can I change her/our diet without her feeling suddenly starved and deprived? When you were a tween and if you were larger, how did you handle it? Momma needs help here!