HELP WITH IPHONE 3 ITUNES SYNC!!!?

sooo i plugged my iphone 3 to my comp to charge it. me and my gf both have the iphone 3 and she also has an itunes account on the same comp. well i wanted to sync the music she has on her account to my iphone. but wen i did that it synced her whole iphone onto my iphone. so now my iphone looks like her phone. and all my info and pics and things arent on my phone anymore. how do i put my stuff back on my iphone?? i need help please!!!! im freakin out!!! :(