I'm pretty sure May's personality is just May's personality. She was more abrasive than she might have been when we first met her because she was in a bad place doing something she didn't want to do as means f reducing the time she'd have to doe something else she didn't want to do.
That said, she cops to having impulse control issues and the fact that she almost took a steaming dump on her get out of jail early card kind of highlights that. May's attitude isn't the result of a poor chassis. It's a result of May being May. Dale has been good for her in the sense that he's able (thanks to his chill factor) to put up with her and still respect her, but he doesn't put up with a lot of her shit. May, OTOH has been good for Dale because sometimes poor control of impulses is exactly what the situation calls for, and she's able to push him into action via a combination of energy and withering sarcasm.
I would wonder if May is really as hateful as the filler implies. It's possible. A lot of her ability to function in the real world has to do with her attachment to Dale. As much trouble as she's shown giving Momo, I suspect her willingness to reach out stems from Momo being Dale's GFs companion, and that's it. Part of it is certainly that May depends on Dale, but the fact that she calls herself May, that her cheap ass chassis still resembles the form that the VR companion system picked for Dale, and the fact that she puts actual effort into making thing smooth for Dale implies actual affection for him.
But if she really is as misanthropic as implied, she doesn't much care for anyone else and Dale is all that's keeping her in check. May could very well be Pintsize without the whimsical humor.
Still, for all the patented overanalysis, I think it's probably closer to the story to say that May is just abrasive, but is otherwise a decent sort of person who would really just rather be a fighter jet.
(Also, of note: good odds that May could not be a fighter jet through normal channels because no one wants a fighter jet with poor impulse control.)