Keep your mouth shut, Kirby. She didn't mean that, and if she did, she was being silly, to a degree.
Quote: but I want to tell her that I didn't expect anything in return, and she should give me credit for doing something nice without any strings attached.
That's a lie, bro (sorry for the 4x4 ) because if there were truly no strings or expectations you wouldn't have a need to tell her even that.
High road, bro, high road.
You're hypersensitive, but there's a reason you feel that way...because while it's good that you were there to help her, it would be better if she didn't find herself in a situation where she needed help for something like that.
I'm not saying it was your fault, cause it wasn't (she's an adult, she can put gas in the car), but it doesn't matter.
From now on, without saying anything about it to her before or after, just always make sure that there's plenty of gas in her car. Treat the half-full mark as though it were empty and when you see it at half or less, top it off.
Start doing things that show you're paying attention and you're taking care of her, adjusting to her and making her life easier...not because she'll love you for it, but because you're the kind of guy who takes care of those details for his family.
You keep using that word. I do not think it means what you think it means. -- Inigo Montoya, 'The Princess Bride'