Ruby's mostly doing what she always tends to do at parties: wallflower. She might break off to the dance floor on occasion if given reason, but for the most part she's hanging around the edges, eating food and watching other people dance. (It may be at least a little because she can't help but feel awkward that she still hasn't held a proper conversation with the woman her father figure just married, a situation that just gets more awkward the longer it goes on and is really her own fault...)

But she still seems to be having fun. She's re-used her prom dress, as it's frankly the nicest dress she owns, and even though she may not dance much she can still be seen swaying and swirling the skirt as she picks away at her food and people watches.