Girlfriend problem.......................… what should i do?

ok so this just happened a couple minutes ago. my girlfriend was telling me her dream from last night and it was about us smoking weed together so ok whatever no big deal. but i asked her if shes been thinking about that latley and she has been thinking about us doing that together and the whole time wev been together shes been totally against drugs and either of us having anything to do with them and that was a big reason she was so perfect to me (im not a goody two shoes or anything iv had a huge drug past and iv just moved on from it and its not me anymore) so i told her that i would talk to her later because i needed time to think and she just said how when i do that it makes it alot worse and how i should just stay and talk to her and i said well i need some to think again and she said about what and i said us. and she was like you seriously need to think about "us" over something like that that i wanted to do WITH YOU becuz it would be a good experience its a complement. so i said yep. and she just said "BAHAHAHAHAHAH ok whatever" so what should i do? wev been together almost a year and breaking up with her has been on my mind alot becuz she is a very unhealthy person, mentally, and she treats me really really horribly and obviously by her last message she doesnt care about me or my feelings or our relationship . but i am so attached and after everything that has happened i havent left after all the break ups and everything imaginable. so even if you tell me to break up with her i probably wont i just need to know what to do. I turned off my phone after her last message