I need help with my iTunes problem?

Every time I go to the app store I'm able to get different apps with MY account but ever since my friend logged into my iPod I can still get apps the problem is now I can't update them with my account they need her password I've tried everything from resetting the settings on my iPod and even logging out of iTunes but nothing has worked so far can anyone else help me I feel like a caveman to technology. -_-