Today she said that I had said something nice, in fact, the nicest thing I've ever said. Read between the lines and you will see that she is really reiterating her view that I am not nice by implying that I am rarely nice (highlighting a "nice" comment by me as an exception) and also by implying that an observational comment that I made is nice by my none-nice standard. Earlier she said she would be happy to see me at club night "if I was nice" - more undiguised assertion of my lack of niceness.
Niceness is an intrinsic quality of sentient beings and to cast doubt on someone's niceness is not a nice thing to do; coupled with a self_description claiming niceness, "nice_squirrel", highlights the fascistic intentions of such claims.
Niceness is not a private club peopled only by invitees. I do not need to proclaim my niceness and I do not need such niceness to conform to someone else's policy-driven definition of niceness.