But as you say, we don't know the situation of dwarf-women. We don't know if they simply choose not to travel or if they're not SUPPOSED to travel (or even if they're actively kept from traveling). If we suppose that dwarves disapprove of their women traveling, then dwarf-women might dress as dwarf-men, false beard and all, as a symbolic "I'm going out into the world as a dwarf-man because I'm not supposed to as a dwarf-woman" gesture. It might not even be a disguise actually meant to fool anyone; it might just be that the public face (literally) of any dwarf is supposed to be bearded, so dwarf-women in public oblige. Dwarf-men would probably even be in on the gig, accepting a dwarf-woman as a peer so long as she kept up the symbolic appearance. But men, elves, and hobbits, not knowing about these customs, would just see a group of dwarves passing by or selling them something and would think they're all men.
I am reminded of accounts of women accompanying men to battles throughout history. So long as they dressed like men and didn't act like women, and took on boys' jobs, everyone could unofficially look the other way and just accept the woman as a boy-soldier.
There are many possibilities, and we don't know which is correct. I'm just looking at the combination of what Tolkien said about few dwarf-women traveling and my own personal belief that Tolkien didn't necessarily mean to have dwarf-women actually growing beards, and finding explanations that fit it.