Roommate Wants To Pay Less

Based in OR. my roommate wants to lower the amount they pay after we asked them to clean up their spare room. They have left cat shit on the floor for weeks. They now said they no longer want the spare room and want to pay equal rent even though I have one bedroom vs two.

They acknowledge the verbal agreement/contract over text and have been paying the landlord the amount they agreed to the past year. It's just interesting that this is coming around the time where they have taken two vacations in the last month.

If they don't pay the full amount next month, will it affect me? Will I be responsible for the rest?

Thanks.