Understand that head throwing and tossing when riding is caused by pain and discomfort, most likely caused by the bit. Either use a range of different bits, preferably light, non-leverage bits, and find the right one for your horse. Or, as Abby says, go bitless. Bitless is a much cheaper option rather than spending £20+ on a new bit, and results in a much happier, more willing horse to ride. Of course, this depends on your horse, however, but research shows horses are more comfortable when riding bitless and show less, in some cases, no signs of agitation (eg. head tossing, tail swishing, stomping, etc).
Personally I would not use side reins or a martingale since this doesn't solve the problem and does not take away the discomfort in the horses mouth.
Good luck in finding the right bit! Or try bitless if you're willing to give it a go!
Hey!!😀 Side reins, my horse was more of a giraffe than a head thrower but I used to ride one who was a head thrower, side reins are wonderful, talk it over with your trainer to get the best fit and exercises suited for your horse!! Good luck!!😊
She might not like the nutcracker action of a snaffle bit. Maybe try a French link bit instead
they work fine for such habits. Snafle or any kind u like. Google it
You could have her checked over by a vet just to make sure there isn't anything else causing her to throw her head (like a lame leg). Or, if you think she's throwing jer head due to the bit, you could try going bitless! Some horses really enjoy a bitless bridle
You could try a martingale if you'd like, or you could lunge her and see if you can see anything from that perspective.