Either short cut hair, or at the very least, done up in a very tight bun, or fairly short ponytail or braids or cornrows or something.

As you say, tangling with the environment or your gear... in a hand to hand fight, you do not want hair that can be pulled or wrapped up, you don't want long hair getting in the way of reloading a gun, longer bangs blocking your view through binocs or iron sights or a scope...

Also... for tampons and pads...?

The 'old ways':

Lint wrapped around wood. Knotted ropes. Papyrus. Paper. Moss. Animal skins.

These were all used before the tampons and pads, with some more ... unique solutions beginning to be mass produced in the late 1800s, eventually leading to modern tampons and pads.

https://cora.life/blogs/blood-milk/what-did-women-do-before-tampons-a-brief-history-of-period-products

So... I guess uh, assuming a post apocalyptic woman's 'survival' stat is high enough, presumably they would return to much more locally sourceable, less complex to produce, decent enough solutions, after the last box of tampons gets looted from the last dilapidated Walgreens.

So... if your character is a postapoc woman badass... you could just add this into your own headcannon as an explanation, of sorts.

... I wonder how many post apocalyptic movies pass the Bechdel test lol.

EDIT: Going a bit further, and arguably off topic...

Common ammunition calibers, cigarettes, condoms, and possibly bandage/compress packs, tampons/pads, bic lighters... maybe also small sewing needle kits?... would be pretty good candidates as physical commodity psuedo-currencies...

Basically for the reason that they are small, light, easily transportable, roughly standardized, are generally durable if stored properly... and are no longer in mass production... and basically everyone would either directly have practical use for them or know someone who does.

Bottlecaps as a currency would represent some level of general social cohesion beyond and above that, lol.

EDIT 2: ... having long hair could ....probably become something of a status symbol, as it would only really make sense if you were not roughing it all the time.

Men would also presumably keep their hair and beards short generally as well, and longer hair/beards could also become something of a status symbol as well.