The snow probably definitely makes it more difficult. Keep up with your bending, and once you aren't riding in the snow, if she is still very forward and cantering, go a few strides, stop her and back. Then go again, keep repeating this and she should start slowing on her own. Once she gets to a lope, let her keep going longer, its not as much work as stopping and backing constantly, then praise her to let her know that is what you were looking for. I have had success slowing horses down like that, without having to really get into their mouths. Sounds like you are on a good track right now.