First of all, don't assume anything and don't talk about cheating, sandbagging, etc. That just makes you look like a busy-body, especially since you don't have a dog in this fight, lol. I know you feel aggrieved, but stalking the kid online isn't doing anything positive for the situation.
As someone pointed out, you want to take the high road at all times and protect yourself and your daughter. You don't want to get a reputation as overwrought or meddling.
I've seen several cases where competitors were on the schedule for an incorrect event. In one case, it was, without a doubt, an honest mistake on the entry form (Pre-Prel instead of Prel) that wasn't caught until the morning of the event. The ref moved her to the correct category before the warmup. The girl and her family are the nicest people, the coach is usually on the ball, it was just a mistake. I didn't say anything when I saw the initial schedule and I wish I had because then the competition would have gone smoother if the error had been corrected earlier. They had to change all the competition lists, posting sheets, make sure the CD was in the right envelope, etc. etc. I was glad the competition volunteers were willing to correct the error, because the skater had worked really hard on the program.
Parents get confused with the titles and the forms and the checklists; mistakes happen. While forms are supposed to be verified and signed by a club officer, online entry has changed that task substantially. Every competitor is still supposed to be verified, but now the competition chair sends lists to each coach and home club. The coaches and clubs are supposed to verify that their skater(s) are registered for the correct event(s). Sounds like that's fallen (no pun intended) through the cracks.
I hear what the OP's saying though: three competitions in the wrong category, with the test passed well before deadlines -- that's wrong. Someone's dropped the ball.
Out of courtesy, assume it's an honest mistake. Don't tell anyone other than the competition chairperson and/or the skater's club test chair. A short note or phone message saying "I think there's a mistake on the schedule - () is registered for No Test freeskate, yet she passed Pre-Prel back in January. I thought you'd like to know as early as possible in case she has to be in a different warmup group."
Don't bring up the research you've done through test results and competitions, and don't write an essay. Two lines is all you need to give them the information and walk away. If anyone thanks you, just say "No problem - mistakes happen." or "I figured it was a typo - glad I could help."
Let them do what they will with that information, you will have done your part. If the skater continues to register for the wrong event, just mind your own business. If others start gossiping about it, just change the subject. Don't chime in with "I told them back in April that she was cheating."
As you've been told before, don't bad-mouth the skater, parents or coach. It just bounces back in the long run, as drskater explained.