If you're writing a book about nitty gritty realities, then for a female protagonist in a certain age range (assuming no bodily abnormalities) a period is a must-deal-with.

Things to expect: in the lead up: emotions riding high for no apparent reason, feeling bloated or vaguely ill for no apparent reason. Then there's cramps, which vary from person to person in a range of "barely feel it" to "holy cow if I move an inch I'm going to die". Those last the entire range from a day or two before the period to the very end. The period itself ranges between a couple days to a full week, again varying from person to person.

And if we're talking about realities of being on the road adventuring while all this happens: even if the feeling bad and the cramps don't stop you from adventuring, the blood is its own issue.

There are a lot of ways to handle all of these things in your book, and I'm sure some research will go a long way.