It doesn’t matter whether her parenting is true or you were same when you were young. This is your house, those are your possessions; you can do whatever the fuck you want with them, and tell others how to use them or dont use them. So you are not the asshole, indeed your sister seem to be the asshole with still coming to your house like a barfaced even though you are not getting on well with her children.

But if you say that you don’t want them anymore if they don’t obey your rules she is probably going to piss off considering her barefacedness.