The Driller is definitely female. Think about this:
1) Flamethrower (she likes cooking!)
2) Bouncy Plasma Upgrade is great at baby showers and to amuse the little ones.
3) Neurotoxin Grenade (she has to get rid of bad perfume somehow)
4) Thinks the Scout is cute, bought him cologne for missions (Pheromone grenade - or maybe this means the Scout is the other female... Hmm... )
5) Mark 2 Driller armor includes a large protective front plate for extra protection of reproductive organs.
6) Titanium Power Drills and Satchel Charges are definitely intended for use in household maintenance and industrial strength cleaning.
7) Several types of armor completely cover the beard, since some female Dwarves do not have as lustrous a beard as others this helps them not feel inferior around their most hirsute colleagues.
I rest my case (and hope I don’t offend anyone.)