They can tell who is multiboxing and who is not. When you're playing with her, she will not be in sync with your toons, will move on her own and so on. I played 4 and my husband played his account as our 5th for a long time, and I know we were reported a ton, especially in the beginning. As long as you're following the rules and not swapping one of hers for one of yours, you shouldn't have issues.