There's a lot of images that come to me when I accept something; greediness (what if my enjoyment is so much I keep asking and embarrass myself by asking for too much?); the person just feels sorry for me; I now owe the other person (like old fashioned cocktail parties where you have to invite those who invited you to theirs) and I'm not sure what I have to "give" that's good enough, maybe I didn't quite understand (in your case I'd think she was paying for them when she might mean for me to pay once she got them for me, etc.) and will be embarrassed in the end in some way.