Re: my daughter
I think the best thing would be to keep working out with her. Yoga and swimming are good, but they probably don't burn enough calories to really make a significant difference unless the person is really dedicated to the workout. Would you be willing to take up Zumba and go with her? I recommend Zumba specifically because it can be a "fun" way to exercise and the participants are generally supportive to all body types. If you haven't done it, it's a Latin-based dance class with simple moves that you build upon. Pretty much anyone can do it, and you'll get a great workout.
Another reason I recommend Zumba is that it is often social and people often leave with smiles on their faces. You can tell they had a good time and they feel better about themselves. This change in mood may make her more willing to make lifestyle changes to improve her health.
If she's eating crap all day, that will need to change for her to lose weight. In today's leisure society, it's it trivially easy to pack on the pounds even if you don't eat crap. Somehow she has to be motivated to eat better. I think a fun exercise like Zumba surrounded by healthy people will help her change her viewpoint.
I would also not bring up her weight or eating habits at all. If she brings them up, discuss them as sensitively as you can. She already knows she's eating crap and is overweight. Keep working out with her and hopefully she'll find the desire to lose the weight.