Partner won’t leave our bedroom because OF my brother

My girlfriend has ADHD and Autism. She has psoriasis and doesn’t wear a bra at home most of the time.

My younger brother is staying with us for 2 months while job hunting. Today, he came downstairs without warning while she wasn’t wearing a bra. She freaked out.

Now she says:

• She’s not leaving the bedroom unless I’m with her
• She’ll only use the kitchen if I’m next to her
• She’s either moving out or staying in the room until she leaves the country
• She’s done talking about it
• The house doesn’t feel like hers anymore

I already told my brother to give a heads-up before going downstairs. He wasn’t trying to be disrespectful, but that doesn’t matter to her.

She says she’s tired of repeating herself, feels like her privacy was violated, and that I haven’t protected her space.

She’s shut down completely. I’m stuck between her and my brother. What the fuck am I supposed to do here?