You can't use the fact that she returned some of the money as an indication of cheating, because it doesn't make sense to ever return the money, even if you were cheating.
It does make sense if you have a guilty conscious and think you just got caught. Giving it back eliminates the financial gain. Now there’s much less of a crime since there was no profit.
There’s also motivation to give someone money if you were honest, like trying to make them happy or go away, but it’s an expensive way to accomplish that and probably less common.
