I told her that she did not have to since I knew she was on vacation. She looked annoyed and said she didn't mind. I said thank you.
I recently had a similar encounter with my W. She paid me back money she spent from my bank account. I right away insisted she didn't have to, but thanked her. I am thinking instead of saying "You didn't have to" right away and invalidating what they did, we should thank them for their generosity. Then tell them something like "Its very thoughtful you did _____ for me, and you really didn't have to, but I am happy you did."
M 33 W 29 S 4 M 5 T 7 11/7/11 Separation, W moves in with parents 12/1/11 W: "IDLY, I'm not coming back, it's over" 1/7/12 D Bomb Dropped