my mare and i have a similar training mishap story.
all was great, i was starting her lightly in 2014 due to her needing to mature more physically and mentally. we'd done walking, stopping, backing, turning, etc in the saddle at a walk. a tiny bit of trotting. she was doing stellar. had a couple of ejection moments that i found out were due to pain she was experiencing. got chiro out, sorted that out, and went back to the task of training. found out mare had been set back further than i thought she would be.
note that every time i came off her it was to the right. took a while to have her be ok with me even tacking her up on the right, or putting weight in the right stirrup from the ground.
they remember. and you have to help them remember that they shouldn't remember.
good advice by all in this thread. let us know how you do with your mare!