It was just an excuse for her not doing something equally charitable. It lets her off the hook, she's not interested in doing it herself and doesn't want to find the time to do it.
I'd take it personally also, I'm thin skinned. It annoys me to no end that I allow thoughtless people's comments to bother me.
Keep thinking, "Like water off a duck's back. It's slides off me and doesn't stop and take hold in my brain"