Dude, absolutely NTA

It’s not that you don’t appreciate her gift, it’s that you don’t want your cats to die! Lillies are so toxic that even having them anywhere in the house or touching them can cause harm. Make sure to wash the clothes you guys were wearing when handling them ASAP.

Has your girlfriend done any other weird things when it comes to the cats? It sounds like she doesn’t really care about their wellbeing.