roommate refuses to leave

Location: Minnesota
I’m dealing with a nightmare roommate situation. She’s not on the lease and was basically a month-to-month/tenant-at-will situation. I already gave her written notice to move out by the 28th, but she straight up told me she’s “not leaving.”

At first I tried helping her out a lot. I let her borrow my extra bed, bedding, storage bins, kitchen stuff, etc. and it turned into her completely taking advantage of me. She’s gone through my belongings, used my dishes after being told not to, taken food/medicine, and her cat constantly eats my cats’ food and uses their litter box. She originally agreed to keep her cat in her room and never does. Her cat chases mine around and stresses them out constantly.

She also hasn’t paid the full rent this month and keeps acting like house rules don’t apply to her. Smoking inside, leaving messes everywhere, unplugging my cameras/electronics, damaging stuff, etc. I even have someone else lined up to move in after her and she literally responded with “well I guess we’ll all live here.”

Now I’m trying to figure out the smartest way to handle this without making things worse. My landlord is aware of the situation and trying to help, but I’m stressed because she refuses to cooperate with literally anything.

Mostly just wondering if anyone else has dealt with a tenant-at-will/non-lease roommate who refused to leave and how it ended up going. This whole situation has been exhausting.