Greens and vegetables are the second most important component in a rabbit’s diet. Hay is first of course. Since your rabbit is now 3 months old, you could start trying some greens. The way to start with greens is to offer one new one a week. You can try a different one the following week, and so on. This way, you can find the veggies that your rabbit really likes and ones that she doesn’t like as much. You have to start slowly and not overload their systems with new food. Otherwise, you could cause a stomach upset. Romaine lettuce or cilantro would be good greens to try first.
Here are 2 links with good info on the best greens and fruit (small quantities only) for a rabbit.
http://rabbit.org/suggested-vegetables-and-fruits-for-a-rabbit-diet/
https://binkybunny.com/BUNNYINFO/VeggieList/tabid/144/Default.aspx
Rabbits need a cage or pen that is large enough (at least 2 feet by 4 feet), plus they need out of cage time every day for play and exercise – in a bunny proofed room, of course. Those small cage sold in pet stores are not at all adequate for a rabbit’s needs. If you go to the BUNNY INFO link at the top of the page, you will see a section devoted to rabbit housing, with pictures of various set-ups.