I am in a similar position...I gave up riding at 14 years old, started again at 22, I ride a broke horse very well, but my boyfriends mom and I decided to get my a 2 year old...everything is going well, but it seems she pushes me further than I am capable of at times. On my mare I am fine, have not come off her, have not gone further than i think is safe and we have progressed nicely.
When I first got back on a horse and everything was different, my weight, my body, my balance.
Like you and your three foot jumps, she had me cantering on a horse with no hands...which was fine until the horse came out of the canter and into the trot where i was focusing on rebalancing myself before asking for the canter again she cracked the whip after the horse came out of the canter and the horse gave a crow hop and a buck...me who was not yet balanced from the downward transition came off, flew into a wall and broke my helmet.
I am the rider who wants to be comfortable in the walk before the trot and the trot before the canter. Anyways I know I need to be able to ride through it, but like you say it is a matter of being pushed too far too fast and so I have just said no to the lunge line and hands free riding for the time being until I am comfortable.
My suggestion, just ask to go down a level. I know first hand that going too far out of your comfort zone can be unsafe, there is challenging yourself and then going too far...if you have a bad feeling there is proably a reason and your horse will sense it as well, so go to where you are comfortable and work your way up again.