I would work on bending her more. Also raise your hands a hair so the bit is acting properly on the horses mouth, ideally you want a straight line from elbow-wrist-bit. Working on bending and encouraging your horse to use its hind end will help her be less hollow. Work on being forward and lots and lots of transitions and changes of direction.
The hands aside I think your eq is great :)
If so, I would take p bit contact, gently touch her mouth and ask her to soften her chin, squeezing with your legs to draw her hind end underneath her and draw her head down. This round her back and activates the hind end.
If she does not flex, start by teaching her to yield to your hand pressure from side to side with one hand until she will give her nose. Then use that to draw her head down vertically from the contact with both hands.