Nooooooo! Don't give her up!! You seem like you care so much with all you have done for her, and if she's feeling down, then a caring friend is what she needs - if you take her back, she could end up with someone who just doesn't look after her, and all your hard work will be undone!
I know that this isn't EXACLTY the same situation as yourself, but my tortoise (Herbie) has worms. I had to go twice to the vets to get him treated. He wasn't eating, he wasn't getting up or moving at all, and I got exactly like you, thinking I was doing everything I could and it was doing no good at all. I had to get him up EVERY DAY, and put him under his lamp. 9/10 times, he'd just head back into his tunnel, and hide, so I'd have to get him up again (this was in summer, so it wasn't like he was trying to hibernate!). I had to hand feed him, as he was rapidly losing weight, and would just walk past - or right over - his food.
It's also worth noting (I know he's not a beardie, but still...) that he seemed to get worse again after each treatment for worms, and it took him almost 2 weeks to seem to come round again.
Anyway, all I'm saying is; that I did this for like 2 months or more. I weighed him every day to see how he was progressing and bathed him (which Horsfield's don't particularly work), but, FINALLY, he has only just started to get up himself in this last week and eat himself. He doesn't do it every day, and when he decides not to, I leave him alone. But he's getting there, and believe me - there in NOTHING more satisfying knowing that you have helped your little critter to get better!!!
Maybe try her on a few other things to eat, as Malibusmom suggested - they all seem to go off things now and then. My little fella used to love watercress, and in the 3 months I've had him has totally gone off them in favour of butternut squash!
Do you have any way to weigh her, to keep an eye on her weight? If she isn't losing any, then that can put your mind at rest a little, as at least she's not wasting away.
Also, I noticed that you said she was scratching a lot before going to sleep... my first beardie used to do this, until I gave her deeper substrate so she could really dig herself in, and then she stopped doing it. What about changing her substrate? You never know - she might not like the tiles?
- Emma
P.S. I know this whole reply post is tortoise-related, but I did go through a lot with my first beardie, so I do have some experience with them!!!