
You can report it to an ra and have a mediation, or you can start being petty. The downside to petty is you will also have to live in the filth for a while, but she’ll learn her lesson. Downside of RA is your roommate will probably hate you and shit talk. But if it’s really bad enough you could also get her fined for the mess so win some you lose some
Get your own trashcan and only take that out, don’t touch hers until she takes it out on her own. Stop cleaning up after her in any capacity. Remove her stuff from the shower/bathroom every time you go in there if it’s a rule she agreed to. Make her live in her filth by not touching it. If you share a room shove everything to directly the line of her side and only keep your side sparkling clean. Down to only sweeping/mopping/vacuuming just your half. If you have a sink move her dirty dishes out