Offering charity to someone can be seen as putting yourself above them socially, and someone could read that as the primary intent. She might see him as denigrating her job. Especially if it is after she just offered help and the he seemed non-plussed.

I don't know if that was the case here. There is a lot of phrasing and body language involved as well, which we aren't seeing in his retelling (other than her own, "face fell," which he manages to read large amount into the same as she might have read (or misread) out of his).