Don’t take away all other food than hay, this method works with dogs because they will eat when they get hungry – bunnies are different. If they don’t eat, their gut slows down and the rabbit loses its appetite alltogether and this is the start of GI stasis, a very dangerous condition that’s deadly if not treated.
Did she eat hay a year ago? She may have a teeth-problem that makes her avoid hay, hay is tough and chewy. How is her poop? If a bunny doesn’t get enough fiber or doesn’t chew it’s food properly, it often shows up as sticky poop or gas.
I had to search for a long time before I found a hay that my buns would eat. I tried lots of hay. What worked out was an organic third cut meadow hay that’s locally produced. They ignore other hay. It can be very frustrating. You should serve hay in smallish wads throughout the day rather than fill the hay-rack to the limit. Some bunnies only eat “new” hay.