Not a woman, but its well known they buy several pairs of "period panties" as to not ruin their nicer ones. This seems to be tapping into that market by making an explicit "period panty" that'll last longer, come in dark colors, has a pad, etc. So instead of buying a cheap set of disposable panties and using those, you'd buy a few pairs of these that are specialized for the task.
No idea how pricing works out. In the end, it might be smarter to just buy a box of 10 granny panties at Walmart for 12 bucks than pay $20 a pair for these high-tech ones. (The 5 day set is $180.) Especially if they can only hold 2-6 teaspoons of liquid. Seems the 'help a girl in the third world' narrative is pretty disingenuous here at those prices. Pads cost a fraction of that. This seems like something a western woman would use on top of a pad or tampon.
Does every startup need to be about "changing the world" and "helping the third world?" Its practically self-satire at this point and was expertly mocked in HBO's Silicon Valley series. This is a luxury good, not a charity.