Friend bought something off of me and now I want it back.....?

A while ago in the fall, I was selling my Rozen maiden manga books at the annual anime club sale. My friend realy wanted them so she bought all 6 for five bucks. Now, I recently looked up the series and got back into it. Now I want my books back. I don't want to buy the smae books again but I don't really want to read online either (I am not very good with electronic scanalations, I have to have paper books) What should I do?