Brian, I have learned from a similar experience to never permit a guest to leave the tip unless I declare the amount. Maybe she didn’t have the cash and forgot her funds were low kind or like you did with the $50 bill. Think, suppose she picked up the birthday tab? Probably would have used a credit card like you did. Also, if I’m with anybody and we’re at one of my regular haunts, I’ll never permit anyone to leave the tip but me. I over tip most of the time especially for breakfast. You did the right and classy thing. I would have overlooked the situation and asked her out again.