Currently Being ModeratedJan 2, 2013 8:01 PM (in response to Kimknott)
Use a different Apple ID for iMessage. Go to Settings>Messages>Send & Receive, tap the ID, sign out, then sign in with a separate ID.
Also, apps and their updates are permanently tied to the ID used to purchase them. If they were purchased with her ID you will always need to enter her password to update them, regardless of what ID you are using for future purchasing (in Settings>iTunes & App Stores). The only way to stop this is to delete the apps purchased with her ID from your phone, then repurchase them using your own ID.