Yes. They do that. It's called manipulation.
Honestly, I can tell you this. Every act of kindness, compassion or human decency on your part will be seized upon and exploited to this person's advantage. You are doing what you think is right because you have a moral code and want to do the right thing, etc, etc.
She doesn't care about any of that. All she sees in those actions on your part is weakness and opportunity.
I know how harsh this sounds, but I've seen all this play out. The next step will be spurious claims of criminal acts against her.
You are 100% right about all of this. I've been trying to one kind and help her out with stuff but she does exactly what you describe. Sees it as a weakness to exploit.
I have definitive proof of a crime on her part, one which would destroy her. I wont share it with anyone unless I have to. Its a last resort.
I won't bang on about it, but I really cannot emphasise enough that you need to act quickly, harshly and decisively in this. The longer it goes on, the more of a foothold she gets and the more emboldened and vicious she will get. It sounds to me like she's still in the raging stage. That can be a bit scary but it's better than the calculating, manipulative stage, believe me. Act now.
My logic is that as we bought it together and have lived their together the house is ours, rather than mine. Had we got married (I refused) it would be half hers so I think she is entitled to the same rights as though we were married- given that it was me that didnt want to get married.
I am sticking with that.