Seems pretty simple, let JC and her Dad waste money on lawyers and court filing fees and what not, have your GF best friend testify that the bunny scarf is hers, have your GF's mom testify that she gave her the vest, and you will be done with it.
Seriously, the burden of proof is on them and it doesn't sound like they have much in that regard, so I wouldn't be surprised IF it goes to court (sounds like empty threats to me) if the judge even bothers to hear your side of the story before throwing it out.
My neighbors accused me of shooting out their air conditioner with a pellet gun when I was a kid. It had been 6 months since they had turned it on but when they did they found the pellets when it wasn't working. None of our yards are fenced, but since it was facing our back yard and I was a teenage boy, it must have been me. We had quite the defense planned out and the judge never even bothered to listen to us, told them to prove it, they couldn't. Judge said "I can ASSUME that he did it, it even seems most likely that the shooter was in [my] backyard, but you haven't proved anything so we are done." Turns out my younger brother was the one who did it, but that is besides the point.