True confession time, I've never gotten into the discworld novels. I know, revoke my geek card but they just didn't work for me.
On the other hand, if you want your elves to be short and chubby while living in trees and baking cookies more power to you. You just need to be clear with your players what your source material and imagery is. So from that point of view, of course female dwarves could have beards. They could just as easily have horns, have rock like skin texture or be 7 foot tall.
The reference to bearded female dwarves in D&D is something I put into the same category. As part of world building the group can do whatever they like. However you should also be aware that some women
are bothered by what they see as a joke and people should be sensitive to that.