Janie, you are right that I should have asked my friend first. Don't know why that never occurred to me!
Chris, there was never any question of lying to her or concealing anything from her. Your and SwordGuy's suggestion of giving her all the money would, I think, backfire; she'd be more likely to refuse all of it than half of it.
Laura, I do think she was glad to get the tub out of her hair (it's a complicated remodel and she's also updating her current house to sell), but I don't feel right about making a good profit off a friend's generosity. I will give her half the money next time I see her.
Thanks, all.
Thanks, all.