I don't know if this is a sensory issues or not. To me it sounds like it might not be a texture issue since it's not just her on the bed or couch that causes the problem. I'm also autistic, have SPD and an anxiety disorder. I have fabric texture issues, but if I can't sit somewhere or have bare skin touching it, then it's just me who doesn't touch it, and it's ok if other people touch since they're not bothered by it. Could it perhaps be more of an anxiety/ OCD related thing? Maybe she's for some reason fixed on people's feet not touching certain things?

Meltdowns can be triggered by anxiety sometimes, and not sensory issues. I know for me, traveling, and having to share close quarters without significant alone time, dramatically increases the chance of a meltdown. Some of my worst meltdowns have happened on trips.