Well, perhaps if you get on really well together, which, by the looks of things, you both do, then you could ask her if she'd like to go out to dinner with you as an informal thing, you know, to chat and the like and so she'd have to eat with you so as not to hurt your feelings (if she's that sensitive), but then of course that might be her only meal, and you can't do that all the time unless you're Richard Branson. Perhaps you can go food shopping together to get some really nice luxury things and try to get her to realise that food is really exciting, equally, if not more so than shoes and clothes. But if she wouldn't get offended, then you can always have a chat with her about her eating habits, but I'd leave that as a last resort. Try what I've suggested first if you like.