What should I have said?

The other day, as I was walking to the parking garage, I was stopped by a woman (who I thought was homeless based on her appearance) using a wheelchair.

She stopped me and said she needed to buy some sunglasses. I thought she wanted a handout and demurred, but she said what she needed was a push across the street so she could get to the shop.

Sure. I had the time. Started pushing her chair to the corner so we could cross. She said she'd pay me for this. I said that wasn't necessary. Took her over to the store. (Twisted my ankle along the way. Figures.) Anyway, when we got there (which couldn't have taken more than three minutes), I ask if she can handle it from there and start heading off.

She calls for me to come back and tries to give me $10. She starts getting pretty belligerent about it, yelling at me to take her money. She's sort of causing a scene at this point, and I just walk away (to the sympathetic eye-roll of a nearby security guard), leaving her screaming at me and waving money.

She says, "My father always taught me when someone offers you money, you take it."

I had nothing to say. I didn't mean to insult her by refusing her offer, but really could not possibly take money from someone for helping her get across the street (even setting aside the fact that, from her appearance, she probably needed that ten bucks an awful lot more than I did).

I wanted to say something like, "My mother always taught me not to take money for doing something you ought to do anyway," but I couldn't quite find the way to phrase it. It isn't that I felt this was charity or anything -- it's just that, I mean, dang, when someone is mobility impaired and they need a little help crossing the street, someone else ought to just help them get across the damn street. It's horrible that she thinks she needs to give people money for giving her a push.

Have human relations gotten so bad that you can't show a little common decency to your fellow man without money changing hands?