Hi oopsy,
Whatever it was, if it was burning,it's ashes by now.
If you have the opportunity to talk to her, tell her what you just told us. What she is doing is unacceptable in your parents home and she neeeds to know she is dis-respecting them and your other sisters.
Go with what your gut tells you as far as talking to your parents, but I would definatly talk to her first, let her know that what she is doing is illegal and her actions could possibly have consequences on the family.
Take Care

#1Texan