Tell her you're worried about making the list too much about you, that you want to be doing things for her too. Then, find out some things you both could do for each other and write those down. It's important that you don't discredit her idea completely, since it is entirely plausible she is trying to be nice with this and will be offended if you shoot down her suggestion. This sounds like something she's already decided she wants, so I would compromise to make it so it's about both of you instead of opening the door for her to possibly be angry that she's doing more than you are. I'm obviously a guy and don't know everything, but I think it would probably be a better idea to make it a 2-person activity if it's something she wants.