AITA for asking my roommates wife to wear bottoms around the house

My SO and I have been putting up our BIL while he’s trying to move back. He’s employed and is paying token room and board while him and his wife attempt to sell their house. It’s been 6 months so far.

My BIL spouse (Tina) is late 30s, a larger girl and some health issues. She’s visited before and ruined decorative pillows due to having “accidents” on them as she likes to sit on our black decorative cushions. Shes now been spending half of every month (and shouldn’t be) in my home, as a guest. She doesn’t wear underwear under her night gown and will stay in her night gown the majority of the day. I’ve had it. I watched her ruin another decorative pillow by sitting on it and leaving vaginal discharge and urine on it. I gave her a day to clean it and she pretended it didn’t happen. I ended up throwing out the pillow in disgust and bleaching the seating mat underneath it. She then wore the same pee stained nightgown the next day and I watched her as SHE LIFTED IT UP TO SIT DOWN bare butt on my furniture.

So we’ve spoken to her husband in hopes that he can tell her to wear underpants nicely. Im also considering getting her a box of incontinence pads and leaving it in the bathroom she uses.

AITAH in this? It’s disgusting right?

Editing for answers: 1. Yep real. I’m audhd and dont react appropriately. I didnt know if I was overreacting or underreacting. These words help. Thank you all. 2. Its my SOs brother, and up until he moved in we (his wife and I) hadn’t spent more than a couple hours together, a day at most. 3. I have a chronic illness myself so have tried to be tolerant and understanding and forgiving. Incontinence is a shameful topic. 4. Size plays into severity of incontinence issues. 5. I do have a pic of the last cushion she sat on. 6. My homes “theme” is earthy colours; blacks, browns, reds, and whites. Yes I have black cushions/decorative pillows 7. The roommate is employed locally, their house is several hours drive away, he’s supposed to be going home on weekends but due to mountain passes, winter weather and illness hasn’t been home in over a month. 8. Its not the first conflict the wife and I have had.

Update: The next morning. BIL spoke to his wife. She now has incontinence pads, and is wearing pants in the common areas and will be leaving today! Thanks everyone for all the responses. I thought I was being crazy for being so upset about this. She hasn’t left yet but soon I’ll breathe a sigh of relief.