Your cameo appearance idea is actually a good move if you pull it off correctly.
First, you shouldn't totally change plans you already have because she doesnt want to be alone that night. Enjoy your night with your friends the way you planned it.
Personally, I would try to make time to stop by and say hello to her and her gf's. Smile, be confident, be C/F...project yourself as a Suave Fella on the move that can't stay because he has prior arrangements.
If you pull this off correctly, you'll leave an awesome impression to her friends. If the friends think high of you and your C/F vibe..it only will help your girl's image of you AS THE MAN. And, if you play it correctly enough where your girl's friends start calling you 'cute' or 'hot' or 'hey..he's a steal'...then your girl will have that thing in her head called desire. Desire built by her friends social proofing you and putting worth in you.
Think about it...if her girlfriends think you're a catch..then she'll want to keep you more because her friends approve..and..in some instances, one of her girlfriends may want you for herself...which will always help to fuel her desire in you.
At the cameo..smile A LOT, be C/F, be confident..