Not pooping enough?

For the past two days I've noticed Nessa hasn't been pooping a lot. Yesterday there was hardly anything in the bottom of her cage (We're still working on litter training.) and today there is even less. Only a small pile. I'm starting to get a bit concerned..
She's still very active and drinking. She is peeing her usual amount, but I have noticed she's not as eager to eat her pellets. She seems to stick her nose up at them and only want treats. (Which I don't give her often, just two a day before bed time.) I recently made her homemade treats (To try to save money. Her regular treats are expensive!) which she loved at first, but now refuses to eat. I don't know if that has anything to do with my problem, but I thought I'd mention it.
Oh. And she has been digging the hay out of her dispenser and peeing on it. I've switched to at least 5 hays in the past month and can't find any she seems to like! I've tried the whole misting with fruit juice, limiting pellets and providing more hay, stuffing it in tubes and balls to make it "fun", etc: But she still doesn't like it. (I'm at my wits end.)
Is her not eating as much hay as she should making her not poop? Or is it something else? I'm pretty confused. Thanks in advance for any advice!

Yes, not eating enough hay will affect their digestion and poop size and quantity. Is she not usually a good hay eater, or is this unusual behavior for her? If you haven't recently had her teeth checked by a vet, that would be the best thing to do. Rabbits can develop sharp points on their molars, and this will affect their eating as it hurts for them to chew certain foods. You'll want to do this right away so she doesn't develop GI stasis and weight loss from lack of adequate food intake.
http://www.bio.miami.edu/hare/dental.html

I would hold back on the treats for now. Sugars and carbs will just further slow down the digestive tract, and without her eating hay this can only make it worse. But she still needs food. Do you feed her any veggies? You can also try soaking her pellets in warm water and see if she will eat the pellet mush. If she just isn't eating very much on her own, you will need to get some Critical Care food mix from your vet, and they will show you how to syringe feed her.

But call up your vet right away and get her in before this worsens. The vet should check the teeth and if there are any problems, schedule a GA to have the sharp points burred down. They should give you some metacam pain reliever. This will help her not be in as much pain and so more willing to eat on her own. The critical care mix, and they may also give you a gut stimulant to help with her digestion. They may also take xrays of her head for dental issues, and her belly because of the lack of pooping.
http://rabbit.org/vet-listings/
http://www.rabbitsonline.net/forumdisplay.php?f=21

Thanks for the reply, JBun. Nessa not eating hay is a normal thing. I've been fighting her on it ever since I brought her home. She seems to only like Timothy Hay, but the people I live with are extremely allergic to it, so I've been giving her meadow grass, orchard grass, etc. All of which she doesn't like. I had the idea last night to sprinkle some dried herbs over her hay and pellets and also sprayed some apple juice on them to encourage her eating more, and it somewhat worked. (I've also cut off her treats for right now.) She pooped a lot more today which was very encouraging. I gave her a large salad last night and she ate it with much gusto. She ate crunchy carrots and (only a few) slivers of radish with no problem.
So my new question is: Is she just all the sudden being picky with her food? She didn't turn her nose up at the hay and pellets when I sprayed them with the apple juice and put the dried herbs on them. I'm leaving her under the care of my neighbor in a few days, and my neighbor is not very experienced with rabbits.. So I'm worried about Nessa doing this for my neighbor.