Yeah, I'll do something nice for her for sure. My problem is this:

If I offer her a mint, she might take it but still not take the hint. I dont want her to just have a mint and then, when she is out with other friends, still have bad breath.

But at the same time... I can't tell her directly because even if she is okay with me, she might be very self-concious when she meets other people and be worried about her breath with them too

I dont wanna hurt her feelings

I think I might say something like, 'I have a brilliant new toothpaste' (Which I do. It is Crest Whitening and it smells great) and suggest to her she uses it. Maybe it may make her breath smell a lot nicer to, as it has with mine.