My mare never took the bit till jumping
You may be riding her incorrectly.
I've gone through this personally and hopefully I can shed some light on the situation.
My TB is off the track and he's done allot competatively and all that whoo haw. So when he was available for sale and I started riding him for his previous owner, he was quite a handful for me.
At the time, I was riding front to back. Hands first - as we all are taught - or accumulate as a bad habit over time.......BUT because I gave him something to lean into, he took it.
I, unknowingly, was causing this very forward, very powerful horse. I remember being out on the CC course, going over a small BN fence and ending up at the other side of the CC field by the time I was able to bring him back down under control.
So at the time, Dorothy Crowell was coming to my barn to give a clinic. She is a Rolex Eventer, Olympic Eventer and readily competes CIC**** and CCI****.
She set up a 3 jump combo. I cannot remember the exact striding, but I remember we took a 5 in 3 and a 4 in 2 - it was horrible. So Dorothy stopped us and took us on 1 on 1.
She taught me to ride Seat into Legs into Hands to soften. Use my seat to control my horses tempo, rhythm, strides, pace - into my legs to aid to lift his ribs/back into me, and lastly my hands.
She showed us how important flat work is, and how to incorporate proper flatwork between our fences, especially for a powerful, forward mount - incorporating seat into legs into hands to soften.
Seat into Legs into Hands to Soften. This is something that every clinitian I have ridden under or audited teaches.
I have a competely different horse now. I am a completley different rider now. I no longer give him something to take, he no longer leans into the bit - because I ride back to front, instead of front to back.
Remember - Jumping is Dressage with Speed Bumps.
My Friend Robyn, she competes Prelim and just recently rode in a Clinic taught by David O'Connor in Toronto, Ontario. He taught his class how to use their seats to control their horses.
He taught Seat Into Legs Into Hands To Soften.
He was able to get on a students horse - with no reins what-so-ever , using only his seat and legs - he was able to bring the horse from a hand gallop, to a canter. From a canter, to an extended trot, from an extended trot to a collected trot. From a collected trot to a lengthened walk, from a lengthened walk, into a collected walk - and finally to a halt.
ALL by using his seat.
Seat Into Legs Into Hands To Soften.
Our seats are SO POWERFUL we must learn to use them FIRST. Hands LAST.
Hope that helps.