Physical attraction is important, but it's not the most important thing. You have to be physically attracted to someone to some degree.
Her personality should be a lot more important, if you like spending time with her than that should mean a lot more than what her looks do. If you two get on well, and there is some kind of chemistry then you need to see past her looks and see her as the whole person (god, that makes me sound terrible).
Personality it ten times more important than looks. You need to be able to talk to the person, get on with the person rather than just think they look good. Communication is the key to all relationships, if you can communicate with them well then why should looks really matter?
She's doing something about her weight, and she'll gain a lot of confidence doing that, hopefully it will make you more attracted to her too. Saying that, try to see past it and enjoy what you two have.