Bumping up the heat and humidity a bit is not a bad idea if you think she's getting sick.
If she's not laying with her head sticking up or showing mucous/bubbles in her mouth then she may just be defensive and hissy. Usually you can tell because when they're sick they lie with their head and neck pretty straight - or straight up - to make breathing easier. When they're being defensive they're coiled up, the neck is in an S, and if you're not careful you end up getting bitten.
If she's hyper-defensive that may be why she was for sale, a lot of people don't have the patience to tame down a snake that is naturally defensive.
I think t might be the early stages of an ri. Someone near by me reached out to me and volunteered their antibiotics, they work as a reptile specialist