Agree with the above, James - you can't force feelings for her when they aren't there. I admire her gumption for asking but you've been very clear with her, so hopefully she will understand and move on.
Maybe you need to speak to your friend Adam and ask him not to encourage her unnecessarily. I'm sure he has the best of motives, sees how hard you are working to lose weight and wants to match you up - but you're not ready and he needs to know that.
Having said all that, it's nice to be fancied - even if it's not by Ms Right (or Ms Right Now lol).