First, you don’t get your horse on the bit – he or she must reach for it. There are a number of discussions on this in other sections – check them out.
As to the mounting issue, you will need a helper in the beginning. Have someone there while you mount, but YOU have the treat (make sure she is aware of it) and don’t give it to her until you are on and she is standing. Once that is accomplished, she has earned the treat, and you give it to her. Vary your routine with her (horses get bored too). Some days, just get on and off. Other days, do whatever it is you normally do. On other days, just have her walk both ways of the ring and dismount. This will ensure that she does not know what to expect, and she won’t start off on her own, but will wait to see what you want her to do. There are probably a million different ways to reach your goal, but this has worked for me with many different horses.
It is never the horse's fault