I think she is telling you she likes you, and that she feels that this is now her territory too. If she’s reaching sexual maturity, then all of this is in overdrive – similar to teenage hormones and it is not abnormal for her to get aggressive in defending “her” stuff.
I know how the whole financial thing is hitting people hard! Sounds like you have a great plan as far as dealing with vet bills in the future. Also check out VPI (vet insurance) It’s around 12 bucks a month. I don’t think they pay for spays/neuters, and they don’t pay for existing or parasitic diseases, but GI stasis and other common illnesses like abscesses that can rack up the bill fast are covered. Saved me lots of money. I pay on the credit card and then I put in the claim. I get reinbursed (70 – 80%)usually within a month which help pay off the credit card when it’s due.
What is her habitat like right now? You have to set it where she has HER definite territory, and then there is the general territory where everyone hangs out and that is off limits to poo! A regular rabbit cage is usually too small for a rabbit to only claim that as their territory. But if you have an xpen, you may have to confine her to that and slowly increase her freedom. You will also need to put her off of the mattress when she starts marking so she understands you claim this mattress.
The challenge you will find though is that because she is not spayed, her instincts to mark and defend may be stronger than any solution that may work for a spayed bunny. Most of the time, a spayed bunny will go through a marking period, but then once they feel satisfied that they’ve gotten their “message” across and they feel safe in their place, the marking diminishes, but with unaltered bunnies, this may be an ongoing battle. With female rabbits, they can fight to the death for the “best nesting” area. This insures the survival of their offspring, so if you find you have a dominate female rabbit, you may have a major challenge. A more passive female will find another place – her pen as the next best thing.
OH…just thought of something. Since she seems to really like the soft mattress, she may be happy with her own litte soft place in her own habitat or if it’s big enough in her pen. I can’t remember they are a called, but they are soft little pet mini-mattress type bedding that go into dog crates. The one I have is a soft foam covered by a waterproof lining and then a soft fleese. All parts are washable! You can find them at Petco I know. I’ll post the link if I can find the product. So maybe if you can make her own place worth marking and defending, she’ll leave yours alone. That may even work for a dominate gal!