Mine would be to do some form of working to ensure that she goes and plays the bastard thing somewhere else - I wouldn’t at that point care if she won the lottery and bought a mansion, met a wonderful lover with a better piano, or whatever: that simple thing of her playing elsewhere would be my aim, and it leaves the channels for it to happen nice and wide so my working can take whatever route works fastest.
She could, as you said, have a really good reason for doing it, which if she was a friend I would think was legit, so I wouldn’t try to bring that in or try to judge her on what she’s doing beyond that fact she needs to NOT be doing it all over MY peace of mind.
I may choose to throw in “without harming anyone” because that’s how I do stuff unless it’s really worth the bother of being actively malevolent. So my next move would be to ask trusted entities 1. who do I approach for this/what method do I use, and 2. do a quick bit of divination to confirm ahead of time that the working will succeed as planned.
Oh and PS I actually did something like that recently with an overweight upstairs neighbour who threw parties all the time and STOMPED everywhere so hard, I was scared she was actually damaging the place.
She left 2 weeks after I did the working, using my “If I was a goddess…” method. I have no idea where she went because upstairs is a shared flat, and I don’t care, but I do know she was supposed to be there until the end of the school year in July.