Mint green works well with pink, if the pink is a pastel. A darker green goes well with a darker shade of pink. This means that you can add more and more green into the room as you transition from pink, and white goes well in both scenarios also.
Again, varying soft greens really go well with pink - but not neon pink or that bright wanna-poke-your-eyes-out pink. Also a lot of girls love a soft lavender. I don't think walls should be painted a bright knock out color. A good soft color is wonderful for walls and they can decorate with all the knock 'em sock' em colors they want--changing their accessories when they want to change the entire look of the room.
I think a light green and lilac are great colours when you are trying to get out of the pink. If you want to try something bolder (you can do it just in one of the walls, so it's not too much), I would say black and lilac (more lilac than black of course)... For instance, big butterflies with several shades of lilac flying around a black background leaving a silver trail behind.