KD, you don't seem convinced she'll keep the weight off. Any particular reason why.......??
Did I sound convinced she would put it back on

Just not convinced she wont, that's all.
No great reasons, but you do sort of get a feeling who will survive and who wont.
A couple of things that I can point to which will make it difficult for her...
1. She was dieting full out for an event. Very understandable and very successful too, but there seemed to be little talk about how she was going to deal with her comfort eating after goal. Maybe she worked on that and they didn't feel it needed including in the programme.
She had a problem that needed sorting. She dealt with the side effect of that problem by dieting. The problem could still be there though.
2. She was more than just a little overweight. Her leptin levels will make it difficult for her to maintain that weight. Possible, but harder.
3. She lost it very quickly, especially the last couple of weeks, which was weird as that's the hardest time however 100% you are. I wondered if she kept her protein up, especially with the amount of exercise she was doing. If she didn't, she's likely to have lost a fair bit of lean mass, reducing metabolism.
4. She will be under huge pressure to keep to goal. That might appear to be a good thing, but I believe it can have the opposite effect after the initial few months as you end up doing it for other people rather than yourself.
Just some thoughts. She might work a way through it all and come out triumphant. I hope so.