Weeell....it wasn't a long rein. And she was not accepting it at all, remaining in the , for her, proper position.
I would have her trot fresh forward, without gathering reins. Have her search for the bit. Then gather her, and again, open your fingers and let HER lengthen the rein( let her chew the reins out of your hand....literally translation from German lol). Once she does it in a trot, try the walk.
She might not quite trust your hand yet.
And you can do that in canter too.
Once she takes the reins by herself, without hurrying, she will nicely stretch into the longer rein.
Im sure the dressage experts here can explain it in more technical terms, lol, nut I just couldn't come up with them....6 in the morning....