It sounds like your timing could be off too.. It's crazy that a seconds worth of indecision or lack of release or cue can do so much to the overall ride. If she is stretching, and your goal is to get her to stretch more, and as long as you aren't dropping the contact (this is the part many forget) then let her stretch. To bring her poll up more, close your legs a bit. Again, it's all about not dropping the contact, I've noticed most likely the outside rein. Once you throw it away she can go all funky inverted on you.
As for losing the forward, try working on bending her, but keeping her out on the 20 to get her back into stretching without losing the forward. Also work on half halts at the trot, compressing the energy and sending her forward out of it to get her better acquainted with the idea of what you're asking of her.
Also, forward doesn't necessarily mean a super fast trot, it also is not a slow ploddy type trot. I like to think of it more as a harness of energy, tempo and rhythm all balled up to make an animated, powerful driven movement. I guess that description works out better in my mind.. This is why I am no good as an instructor ;)
Keep up the work and good luck to ya!
We are not human beings having a spiritual experience. We are spiritual beings having a human experience. -Pierre Teilhard de Chardin