Yes, probably just a nervous passenger...don't be too quick to judge. Had the same thing a couple of years ago....a passenger had a mild panic attack as we were taxiing out...the cabin crew tried to calm them down but they was determined they didn't want to travel. No fault of theirs - they could have been having some emotional trouble and maybe it all came to a head there and then.
What are you going to do? You can't keep somebody imprisoned in a long metal tube for hours when they're in no fit mental state to travel as it isn't fair on them or the people around them. Plus, there may be a legal liability arising if you ignore somebody's request for help. We came back on to another stand and it cause a delay, but IMO it was the right thing to do.
You can't "blacklist" somebody for having a bad day. It they were doing it out of mischief then yes, but not if they're not well enough to fly. Maybe this pax just needed a few days to get herself sorted out prior to travelling, not just one?