Daughter had a friend (note the use of the word "had"). Friend trained with BNT who was the "only" trainer who understood her horse. Swore that she had to ride fast (dangerously) in order to jump him. Swore that no one else knew how to ride her horse but her and BNT. Another trainer recommended she move back down to Novice after breaking her ankle in a fall. She insists on competing at Prelim Eventing and has never completed a prelim event. She's either withdrawn or fallen off (fell off the back of the horse at the last show jumping round she competed in). There is no reasoning with her.
If the BO or BM won't interfere, I would just close my eyes and not watch and make sure you stay out of her way.
Tell her she did FANTASTIC over one of her better jumps - something like the horse liked that ride much better and his head didn't go up in the air so much. That she is getting the hang of a release, etc. That will make her think and try harder?
I put things into the category of "Am I being a moral coward by not saying anything." If the answer is yes, then I'll say something. I don't always believe MYOB is the best thing. Not enough people care enough.
The best policy? Mind your own business. It's not like she's killing her horses. If she is as horrible as you say, the horses she rides will start stopping and then no more jumping!
I think it's fairly safe to say if you invited her to take her and her horse to a clinic you are riding in, that would be Ok. If she declines, maybe ask her to come audit. Some people learn a lot from osmosis learning and replicate easily what they see. That may get her interested in a formal riding education. Otherwise, leave it alone unless you want to be seen as meddler and not a very good friend.
I would also mind my own business. If she is doing things as terribly as you describe, her horse will stop jumping. If she's getting around a 4' course on a regular basis she's probably doing just fine.
I have seen *many* people jump small jumps in draw reins to deal with different issues -- they are not really a danger if you run them to the girth billets or up through the breastplate.
When people are riding in ways that scare me, I avoid riding with them (if they are making me anxious *my* horse picks up on that!) and if they really make me cringe I go into the barn or whatever so I don't have to watch.