I am also bonding my first pair at the moment.
I adopted a second bunny (bigfoot) this past Sunday and have been experiencing similar behavior.
Although my other rabbit (oreo) isn’t displaying any aggression I do sense that she is jealous whenever I tend to the other rabbit.
For example whenever I pet Bigfoot Oreo approaches and puts her head down for me to pet her.
If it makes any sense it’s possible that she is feeling neglected even if you may not be neglecting her.
Before you got the second rabbit she was your only child and now she has to share youb

my advice would be to give her some time to form a bond with the other rabbit. This will hopefully allow her to come to terms with the fact that you are not exclusively hers anymore and she will hopefully accept that and learn to share.

As for the biting, it seems she bit you by mistake? It’s in any case not cause for alarm when it’s a rabbit. Dogs must never bite humans, especially not bigger dogs – they have been bred not to and we consider it totally unacceptable if a dog bites a human “right out of the blue”. We still have to teach puppy dogs bite inhibition, even though they to an extent have this inhibition bred into their genes after living with humans for about 40 000 years.

Rabbits are far less thoroughly domesticated than dogs. We’ve kept rabbits as house pets for a very short time, practically just a few hundred years if even that long. That means they still have a lot more of the wild rabbit in them. Your reaction to her bite was good – she doesn’t seem to have gained anything by biting you, and that is vital, because animals, humans included, learn by trial and success. In short: If something works, you keep doing it. If something doesn’t work, you try something else if you’re reasonably clever. Most rabbits are reasonably clever.

I do think Kramer makes a good point about your girl being “jealous”. You are an important resource, you bring food and treats and pets and toys. Now there’s another rabbit competing with her over this important resource. She gets angry, much like a young child that gets a sibling.

What you describe is exactly how my bunny Yohio was when we started to get to know each other! He growled and lunged and boxed at me, then immediately put his head down for pets. I think it’s about conflicting emotions, at least that is how similar behavior in cats is explained. The survival instinct (which is strong in animals that still have quite a bit of “the wild” in them) says: Danger! Attack! And then there’s another part of the brain that goes “but head pets are really nice…” With my Yohio the niceness of head pets gradually won over his instinctive fear.

The one intruder he never came to terms with was the broom. Horrible broom came into his area and stole his poop and leftover hay. Horrible broom often got a good beating, but it never learned.