My sister came to stay and has now left. She used my windows live to get in her hotmail (I use gmail) but now I cant log her out and me in. I have somehow got all her 1500 odd contacts in my contacts and I dont want them there. If I delete them I guess it would delete them when she wants them too so I just want to log out of hers, but how?

How can I just reverse this , back to my own gmail via windows live and without deleting all her contacts please?