Rabbits are grazing animals, so they eat throughout the day. Just make sure to supply her with the hay you can get and she will eat what she wants. I notice my own rabbits go through different phases; sometimes they eat SO much hay and other times they don't eat so much. The other thing is if there is old hay in there mine at least get reluctant about eating it, so make sure there is always fresh as well.
Looking at your picture (she is adorable by the way!) she looks like a Californian. Is that her breed? I know Californians are known as meat rabbits (maybe you already know this, sorry) but since they are bred for that they are on the bigger side. If you know her breed (even if she isn't exactly purebred) you can probably google a proper weight for her breed and weigh her if you can. When I weigh my rabbits I just weigh myself on our scale and then I weigh myself holding my rabbit. Or you can use other tells like what people have said about feeling her spine.
Sugary carrots certainly can put weight on rabbits and grain will too, so I agree with others to put her just on hay, and I also suggest pellets--but in a small amount. You never want to feed too many pellets since they can add weight too. Is your bun a pet? If so, for a pet I see pellets as a supplement--it has good stuff in it for them but should be fed sparingly. My two rabbits, one a 4lb and the other 5 and a half lb get half a cup of pellets per day. I think for one rabbit people usually suggest a quarter cup, although I saw someone above say half a cup for medium sized breeds. I'd honestly go for a smaller amount though if I suspected my rabbit to be overweight.
I agree with others that putting her on a balanced diet of hay and pellets is a good idea if you think she's overweight--that'll get her on the right track. And when giving treats (later after you think she's lost weight) I'd suggest giving in small amounts and/or infrequently.
So long as you supply fresh hay daily as well as pellets she won't go hungry. Hope I haven't said anything you already know--sorry if I have!