Warn her if u do that once again u will get into a lot trouble
and tell that u have ur eyes on her and the next time she's over
tell her that u have clear evidence and next she will be at the police (even though just don't do that for real)
warn her if she don't listen put it into action
Oh wait. Is rupies money?
You live in Hyrule?
Try recording her on webcam. Can't argue with that.
Are your rupees worth more than your sister?
The above answer is swell.