iPhone shows it's charging but the percentage is dropping

I am at a loss right now.

When I plug in my fiances iPhone it shows that it is charging, the green battery shows up, the battery icon on the top of the screen has a little plug in it just like it's charging but the battery level keeps dropping.

I have already restarted the phone, I performed a basic reset and I just finished wiping and reseting the phone to factory settings.

The problem persists.

Any ideas?

(btw, this problem started showing up last night and she updated her iPhone to 5.1.1 two days ago.)