Don't feel guilty at all! Obviously she wanted you to have it.

Short story....
One of the girls I work with was waiting on a couple that had just gotten back from Vegas. She's quite a talker and chatted with them most of the time they were there (telling her about what a good time they had and all). Well there check was only around $75 and they left her a $1000 tip
So no, I don't think you should feel guily one little bit