Oh I'm glad she's already spayed! I didn't know what the situation is, since a lot of people get bunnies and come on here with no real idea of gender, age, spay/neuter, etc. Having bunnies for the first time can be bewildering and there's a lot of contradictory information out there. A lot of people wind up at our forum VERY confused! I know I did!
But reading a lot has helped me gain some good rules of bnny care.
You can keep her on alfalfa pellets if you like, but I'd start switching to a good timothy pellet. Make sure any changes are gradual. A good pellet won't have seeds or "lucky charms"-looking things in it, it'll just be brownish pellets. Oxbow Bunny Basics T is good, as is Zupreem Timothy. If it's the only timothy pellet you can get, Kaytee Timothy Complete will work too. PetSmarts have started selling the Oxbow pellets and hay, which makes me so happy! Other smaller local chains may sell it too.
Start introducing veggies from our safe vegetable lists. For reference, my guys are each 4-5lbs and they each get 1/8c Oxbow BBT daily, along with 2c veggies (1c in morning, 1 in eve). My bf's little bunny Benjamin is a bit younger and very active, so the 2.5lb bunny gets a little less than 1/4c Oxbow BBT and 1c veggies a day. Gradually switch to the timothy pellet, then gradually decrease to around 1/8-1/4c.
Has she ever had a fecal float done? This is a test for intestinal parasites and I think it's a good idea for a new bunny coming from a petstore, breeder, or shelter environment. Some people don't think it's all that great, and if you got her from a great shelter, they probably did it already.