Thanks. Rabbits will often choose pellets over hay. Do you limit the amount of pellets per day?
Plain pellets are healthiest. Those that have colorful treats mixed in are junk food and can easily discourage hay eating. I suggest looking at switching to a healthier pellet. You can check here for recommendations:
http://rabbitsindoors.weebly.com/pellet-food.html
Don't switch suddenly though. Transition slowly as explained at the link. As she's slowly transitioning, you can also begin cutting back gradually on the amount she gets (if you aren't already limiting). An average size rabbit (5-7 lbs) should get about 1/4 cup of pellets per day.
Cutting back on pellets and feeding pellets that don't have treats mixed in, should encourage more hay eating. Skip treats totally for now. (Those rice treats from Petco are also not good anyway)
I'd check the hay you have. If it is older or dusty, she may not like it. They also like hay best when it is first placed in their cage. So don't wait for her to finish what she has before adding fresh hay. You can add new hay 2 or more times per day. That often serves to encourage hay eating as well.
If that doesn't work, try different types of grass hays. Bermuda, oat grass, orchard grass, brome.. are just some options.