Ex Friend Making Me Pay Back The Holding Fee We Spent Together

I’m a student, and I was in a friend group where we were going to rent a house for the next academic year together. Honestly, these people were toxic and treated me like shit. I’m not friends with any of them anymore so obviously we’re not going to rent a home together

The problem is, we made the decision together to put forward a holding fee for the house. I paid though my bank account. When we lost the two other people we found to rent the house with, we decided to split the money between the three of us. Now that we’re not friends, they’re expecting me to be responsible for the full amount. It was non refundable and though I’ve found a new group to rent with, this would mean the £750 would come from just me.

The first friend that contact was cut with threatened legal action, so I caved and sent the money back. Now it’s just split halfway with friend B, and I just got this text from them:

Hello, Could you pay the £375 you owe me within 14 days (by 16:00 on 11/05/2024). If you fail to do this, I will take it to small claims court and/or the police

What the fuck do I do? I want to respond saying: “Hey, it wasn’t refundable and we both made the decision to put forward a holding fee. It’s not my responsibility to pay the full amount”

But do I just cave and send it to them? I need to do all my uni work in the next couple weeks and honestly I don’t have the capacity for this, but I really can’t afford it

Edit: just want to add that she’s the who decided she didn’t like me anymore and cut contact. So even though it was a huge relief for me as I have problems cutting people off, I did not kick her out or put her in this position