It is normal for girls to wet or pee in their panties?

i don't exactly think it's "normal".

Of course i can't speak for others, but in my experience, that's also a rather specific fetish.

While a number of girls definitely enjoy's watersports or playing with pee in some way, soaking your own panties is something different.

As in, i like the feeling of having warm wet clothes on me, wether i peed in them or someone peed on me, but many of my accomplices in this preferred being in the nude themselves.

I assumed you meant this sexual despite writing it under "habits", because even as a "habit" there would have to be a motivation.

As in, i don't go out and try getting drunk until i pee myself by accident as a "habit".
If you are, however, really talking about wether it's normal for girls to have accidents without any kind of background: Many of those i know had one at some time, but mostly when they were dead-drunk or passed out.

Some also have one by choice(e.g. instead of undressing and squatting down next to a busy street while it's raining anyway)...

I'm a 53 year old guy...No, I don't think it is normal for a girl to pee in her panties, but I do know of quite a few women who have done it...I suspect more than half of adult women have done it since they've been potty trained...people do make mistakes...I pee in my pants about once or twice a year, though never on purpose...

I'm gonna assume you don't mean in a sexual context, so both angles are covered.

I'm not a girl though, but I have met some. :P And I don't mean sound creepy, but women don't have quite the bladder control men do. It seems having a small accident from sneezing or laughing is not a super rare event for them. Obviously the risk is greater with a full bladder, and pregnant are especially susceptible.