Like Luna said, is she eating and drinking her other things? If not, I would check her tummy. Especially if it’s been longer than 24 hours (in that case it’s considered an emergency).
If she IS eating other things, than it could just be a phase. Sometimes my bun does the same thing. Sometimes he inhales his hay, other times all he wants to eat is pellets. I just stick with the normal routine and he goes back to it. I have found that in times when he goes a long time without eating his hay (say a couple of days), I will give him a different brand or type of hay (something sweeter, usually) just to encourage him to eat it and to keep that roughage in his diet (even though his pellets are timothy hay, it breaks down differently). Then when he eats the sweeter stuff, I’ll start mixing in his ‘old’ hay until he’s back to eating it again. It’s sort of like tricking a fussy kid into eating their veggies! 