Hm. Well, I will tell you that my son when he started the first grade had a period of time that he was wetting the bed again. Due to stress.
It wasn't 'on purpose'.
If you are saying that you feel your daughter wakes to pee at night and then sits there in the dark and grins like the grinch and says "hm, I'm gonna show mom!" and pees 'on purpose' and then lays back down waiting all night just to really tick you off when you see she's peed in the morning--- wow. I doubt it. But if you really feel that way, your best bet is to perhaps take her to a child psychologist to work on this.
Because whether she is now doing this out of habit, out of laziness, out of spite or whatever, she is still having some sort of issue that deserves empathy. By this I mean, if you feel her mental health is such that she'd come up with this pee plan to drive you nuts---- then she would most likely need some mental health care and your concern rather than anger.
lots of luck and I hope she finds her way.
Ditto what specialmom says. Especially mothers with new babies often write in about an older kid who has broken their potty training, often implying that the kid is doing it deliberately and willfully. When a 6-year-old has a problem with potty training, almost categorically they are reacting, and responding. Not coming up with something out of the blue to punish you or make you mad. She's got stresses in her life. Put her in night diapers until you figure out what they are, and find ways to ease them. As special said, take her to a therapist if you think she is really out of the norm. How calm would you be if your husband had brought an attractive new woman into the household and put her in a bedroom down the hall ten months ago, and chided you if you felt hurt or jealous? That is what a new baby can feel like to a kid who has gotten a lot of mommy's time and attention before, an interloper (and a rival), and it can get worse as the baby gets cuter, before it gets better. Try hard to work out ways to solve the issue and in the meantime make it easier on yourself with night diapers and disposable incontinence pads so you won't be so mad at having to wash sheets.