<human>: My girlfriend and I live together with multiple roommates, there are no guest rooms, guests generally stay on the couch. We both live away from our families and love to talk with them when they visit.

A few months ago my brother visited and I knew we would probably have a few drinks, play cards, chat, etc. so I figured me and him would sleep on the couches. This way my girlfriend could have the bedroom and go to sleep whenever she wanted. She agreed, didn't think twice about it. 

Now to present day, my girlfriend's sister randomly called and wants to visit soon. While still on the phone with her sister, my girlfriend says she would love if her sister could visit and we'll make room by having myself sleep on the couch. This way they can stay up late, have a few drinks, chat, etc. When she gets off the phone I tell her I don't want to sleep on the couch, she and her sister can take the couches and I will take the bedroom, exactly as we had done before. Her response, "[sister's name] is a 25yr old, married women....those couches are disgusting..."

And she is now mad at me, presumably until I let them have the bedroom. I mainly frustrated not because I care about where I sleep, but that she, without hesitation, relegated me to the "disgusting couches" whereas I, without hesitation, gave her the bed when my brother visited.

Can you provide a brief rundown of the text in within 3 sentences?
<bot>: Girlfriend's sister wants to visit, girlfriend relegated me to the couch...how do I show her the inequity between our two responses?