Sounds like she has already set herself up to fail.

Her success isn't dependent on others. Which is perhaps obvious and frustrating to you. It's tough reclaiming identity after a couple decades of total immersion in family life. Of course you are supportive, it's that support doesn't require you holding her hand.

Personally, I look forward to small moments of me time. Which is where she needs to get herself to.

Sustainable weight loss is a long process, I would know.

How to handle this? Realize that while she's feeling low about herself, she doesn't seem to have that inner child of hers comfortable with newfound independence. End result is that emotional blackmail.

Not sure about food? Many family members will eat in quantity.