Hmmm...well I didnt read the other posts as I couldnt be bothered to. So it seems you either need to get him/her off the forehand a little, or you are putting too much pressure on the reins and not using your legs enough. Impulsion comes from the HQ not the front quarters. And also If you are using the pelham, and its too severe, she will most defiantely lean to try and get away from the pressure.
Again, sorry if this is all repeated.