i find it really interesting that terezi is characterized at first as being facetious with most of the silly shit she does, only to show later down the line (with all her grief over latula being "cooler" and more "confident" than her) that this was mostly just deflection due to her insecurity with being herself, with being weird uncomplicatedly. she's a very layered character who likes to be openly odd and off-putting and fuck with people and yet is still sort of reliant on their respect for her as a person with feelings, and doesn't like when she doesn't get that level of understanding from people. loves living by the bit, cannot stomach dying by the bit
it's like.... when terezi projects a strong image of herself, it gives her control of the situation and of how people see her; she gets to be the one to build and define the reality around who she is, as a sort of scaly, iridescent hide to protect her soft and mushy core.
when she roleplays with nepeta, she tells herself she's doing it facetiously, as if she has something to prove by doing so and not that she just enjoys playing in the space with a friend who similarly delights in skewing the lines of identity. having to face the truth of the matter — terezi having a deep and embarrassingly genuine personal connection with her lusus, and the things that implies for her true identity — would be far too difficult.
when she messes around with karkat and later dave, she uses an abrasive and flirtatious mask as a means to assume control of the social battlefield, in order to keep things in a realm she deems comfortable. ultimately, this leads to both her and their feelings getting hurt when they try to get any sort of realness from her and she shies away due to her learned fear of intimacy.
when she flarps with vriska, she claims to use it as means to forward a personal and sanctimonious ideal of justice, but finds herself backing away from it all when it turns out her code of morals is faulty in the wake of material circumstance, of vriska needing to do terrible things just to get by. when her control over the perceived reality of things fails her she would rather run away than be forced to admit why she really wanted to be a part of all this — if it ever came down to the knowledge that she was only ever in it for her attraction to vriska, it would be far too damning in all the ways she herself has constructed. she'd be a criminal, through and through.
terezi always keeps this distance, detaching herself from things in a way that lets her be able to bail when it gets too real, and never look guilty in doing so. she's so deeply scared of being herself and being rejected for who she really is that she will pretend she doesn't like the things she does/put on a show of being a weird and alienating freak to discourage eyes that might pry further into her/die on the hill of a false ideal taught into her by the legacy she lives under. all of these things lead her so far from the truths of herself that it gets her on the wrong end of her own blade for her trouble.