i can't decide on whether i would rather have dwarfettes bearded or no...
DnD they are not, LotR they are...
if female beards are toggleable, well, i have no idea what to do.
In WoW they aren't..... so thats 2 against one.
D&D and WoW hardly count, as they're largely LotR ripoffs anyway, so any instances in which D&D or WoW differ from LotR can simply be considered errors on the parts of TSR or Blizzard respectively.
As for LotR itself, I don't think there's anything in the main text discussing female beards, or even mentioning female dwarves at all--the only dwarves that even make an appearance are Gimli and (briefly) Gloin. Female dwarves are mentioned in The Hobbit (Fili and Kili are sons of Thorin's sister, I think), but that's it. However: the extensive appendices to LotR do state, if I remember correctly, that female dwarves are visually indistinguishable from male dwarves to the extent that most of the aboveworld races don't even realize that there are female dwarves, so that could certainly be read as implying beards.
In any event if we want any sort of realism the question we should be asking ourselves first is: why DON'T female
humans have beards? And why do male humans have beards? My guess for males is that a thick full beard is a show of healthiness and excess resources (protein), much like a lion's mane or a peacock's fan, although in all three of these cases I'm not entirely certain why females don't have corresponding structures.