I would most definitely attribute this to rabbit “puberty”. Her age is about right, She appears a smaller breed also and they sexually mature earlier then the larger breeds. Experienced vets will do a spay at 4 months old, that’s not unheard of. More commonly it is done at 6 months old.
The smell is likely a combination of her urine (now that hormones are present) and fecal droppings. It sounds as if she is doing some territorial marking with those and they do have an odour to them. They coat it in a secretion that smells.You’ll notice they look slightly shiny – but not as shiny as cecals.
You tend to see a lot of attitude and vying for dominance when a rabbit reaches puberty. They may not want to come out of their hiding spots, growl and pounce at you if you intrude, and yes, bite. They can become “cage aggressive” where they’re not really tolerant of anyone messing with their area and will go for anyones hands coming into there. They basically become a grumpy teenager and it sounds like your girl is using biting as her defence.
Both bites were not enough to leave a mark and were more warning bites, but i’m worried that it’s a bad habit that she may soon develop.
That is quite possible, so when she does bite, it’s important not to give her what she wants straight away but also, not to aggravate them further. For example, if she nips when you hold her as a way to be put down, do not do that right after. Otherwise she will learn biting gives her the result she is seeking.
If my rabbits nip, I usually just give a verbal reprimand and stand my ground. Sometimes I quickly push the head down. Sometimes you can let out a squeak like another rabbit would do.
Mostly, you just have to avoid putting yourselves in situation where she is likely to bite – as much as possible. ie. If you need to clean her cage, do it when she is out and about.
One of the triggers for my single rabbit is the scent of my other pairs. So when I walk in the room after I’ve been in theirs, he attacks my feet. Most of the time I put slippers on to avoid that happening. For the times I forget, i have to stand very still and I prompt him to go to his box so I’m able to step away. Lol. If he nips, we have a little stand-off. I give a reprimand and sometimes will tap his butt so he hops away.
It sounds like she’s getting a bit of the cage. If you cannot let her out as often, consider investing in an exercise pen you can attach to her cage. Then you can leave cage door open so she can come and go at her leisure.