You cannot put another rabbit with Bella until she is spayed and recuperated and the new rabbit also has to be spayed or neutered. It would not be safe at all for Bella or for the other rabbit.  You cannot just put any 2 rabbits together, they have to go through a bonding process after both are spayed or neutered. You are right to be scared of fighting. Rabbits can severely injure each other when they fight, as you have found, and it doesn’t matter what sex they are – all of them have to be spayed or neutered before bonding can take place. Spay surgery can be expensive. Would your parents be willing to pay for that? If not, and assuming that you don’t have the funds for it yourself, you would not be able to get another rabbit to be a companion for Bella.

Bonding can sometimes be quick and easy, at other times it can be difficult and take weeks or even months, and in some rare cases, the rabbits never get along and have to be kept separated. Since you don’t have that much time to be with Bella, you probably wouldn’t have the time it takes to bond them. Plus, Bella, would need after care after her spay surgery, and the new rabbit would too, unless you got it from a rescue, which would mean that it would likely already be spayed or neutered.

Here is one good article on bonding: http://rabbit.org/faq-bonding-multiple-rabbits/

I hate to keep sounding negative, but it’s generally recommended that you don’t house rabbits and Guinea pigs together. This is due to different diet needs, the disparity in their sizes (although you have a smaller rabbit) the fact that rabbits are stronger and have powerful back legs that could possibly injure a Guinea pig, the fact that a rabbit might intimidate a Guinea pig, and the fact that rabbits can carry a bacteria which can be passed on to the Guinea pig and cause a disease.

A very experienced rabbit keeper told me the girls can be worse fighters than the boys. They can badly damage other rabbits including grown males who enter their territory.

Do not put one rabbit into a female rabbit’s territory. Have both spayed and get a new cage.

That being said I have a female cat bonded to a female rabbit. Cats though are a 15-20 year commitment.

We rescued our girl from someone who had tried to bond two unspayed girls together. Betty ( our girl) got severely injured and had to have surgery. When we got her she had just recovered, and had a completely bald leg. I think this was partially due to the fact that they were two un-spayed girls, and partially due to how the former owner had tried to bond them. We then spayed her and spent the next few months bonding her with our Buck. They are now happily bonded though! I would never bond two that are not spayed!