Thanks for taking in this bunny. When you make a switch in pellets, it’s best to do so gradually. The first week, mix 75% of the current pellets with 25% timothy pellets. The next week, you can mix them 50/50, the third week 25% alfalfa pellets with 75% timothy pellets, then all timothy pellets. Rabbits love their alfalfa, so hopefully this one won’t pick out the alfalfa and leave the timothy pellets. You can also try some other varieties of hay. Most rabbits like orchard grass, since it’s a little bit sweeter. There is also oat hay, meadow hay and other grass hays that are good.
Start very slowly with greens. Try one new kind a week. Romaine lettuce is good to start with, or maybe cilantro. Most rabbits love kale. If you can find good, fresh carrot tops, those are always a treat for rabbits.
Here are 2 good articles on veggies/fruits:
http://rabbit.org/suggested-vegetables-and-fruits-for-a-rabbit-diet/
https://binkybunny.com/BUNNYINFO/VeggieList/tabid/144/Default.aspx