ACK! That’s a new one! And to think I have a couple of cups on my desk as we speak and I was just about to paint my nails!
Hmmm…I can’t be certain with cups, but when I drip nail polish on my silicone cutting mat I can let it dry and then peel it off. I’m guessing you tried this? 🙁
Maybe try boiling the nail polish off? I wouldn’t use acetone. It’ll probably eat away and deteriorate the silicone o.O
If you can get the nail polish off by peeling or boiling, I would still soak it in Hydrogen Peroxide over night.
However, I would probably invest in another cup just in case (or for back up).
Good Luck! 😀