How should I tell my best friend...

My best friends birthday is tomorrow. She wants to go somewhere out of town with myself, my husband, and her SO. I assumed it wouldn’t be an expensive trip but with all of the activities she’s planning it will cost my husband and I over $275 and that’s not including staying a night at a hotel if we don’t want to drive back late. On top of me having anxiety, and recently it’s been through the roof due to us looking to buy a home/spending lots of money on a home. It’s tomorrow and I don’t want to hurt her feelings but I can’t afford it, also I don’t want to have anxiety or an anxiety attack while I’m there and have to leave to sit in the car, etc. she’s really sensitive but I love her and don’t want to hurt her feelings. Please help!