If she is that young, then yes, a young rabbit formula would be best. There are several kinds out there. They are alfalfa-based instead of timothy-based. Alfalfa provides them with what they need to grow. Once they are done growing, then they need to be switched to an adult formula.

Alfalfa hay can be given in combination with the pellets, but many find that it isn’t necessary. Plus it may be harder to switch to grass hay once they are older if they are used to eating alfalfa hay.

Babies can be free fed pellets. This is within reason, of course. But most babies will eat whatever amount their body tells them they need. Just monitor her intake to make sure she isn’t consuming an extreme amount.

Babies should not be given veggies until they are 12 weeks. At 12 weeks, you can start to slowly introduce veggies. Start with simple things (romaine, etc.) and introduce them one at a time to make sure nothing upsets their GI tract.

Are you feeding her adult pellets now? You should probably ease into the transition. Alfalfa is much richer than timothy.

Yes I would do a very gradual transition!

Echo’ing the others, yes, slowly transition her to the appropriate diet and be sure to eliminate all veggies from the diet right now, as the gut is not mature enough to handle it.

Separate from your question, I do want to highlight that you need to keep your new young rabbit separate from your first rabbit at all times. If there are intentions to bond them, you cannot start any “dates” until both are at least 1mo spayed/neutered.