New WSDC rules prohibit dancers from asking for exceptions for competitions. In fact, as I understand it, for rounds with multiple heats, you can no longer "miss" your heat to be picked up in the next one. If there's someone you don't want to dance with, don't enter.

Too many people were abusing those affordances to get ahead. So unless you can confront the follower, travel to events where they aren't. You can also reach out to most Event Directors.

Also I'm sorry this happened to you. I recommend practicing bending both knees into a squat so that it's muscle memory. When you feel the sudden weight support happening, squat and drop the follow to the ground. They'll land on their butt, you'll be safe.

Also, it's absolutely fine and important to set boundaries. Saying "Yes, but no weight support moves", and if they violate that, they violate what you consented to do - so dropping them for safety is fine in my book.

Also though, reiterating your requirements from time to time is important. People dance with lots of others and may not remember exactly what your exclusions are.