Sometimes lesson horses are just that, horses that might not bond with people, but don't mind who gets on their back.
I have hardly any relationship with my Soldier. It's strange to explain. We have been riding together for almost 10 years and I can think things like, "we'll take that jump after we go around this bend" and he'll pop into a canter and do exactly what I thought with minimal guidance. It's great! BUT, he doesn't give a dang about me cuddling him, doesn't care to stand to be brushed for as long as I would like to brush and coddle him, he'll ride with anyone on his back. We have no "bond" and although I love him and we have great rides, he is not, nor will he ever be a heart-horse. I am ok with that. You won't form a bond with every horse you come into contact with. And that is ok. I think you are trying to make this too human. Learn what you can from her and don't think too deeply on whether she likes you as long as she's safe.
I traded my common sense for horse sense.