First of all, the vagina does not have any hair. The hair is on the vulva, which is well outside the vagina. Urine does not get there but stay in the vulva which covers the urethral entrance (pee hole) and vulva).
Acording to your own reasoning, not having hair will bring the urine in direct contact with the skin. So instead of these few drops being caught in the hair, it is now on the skin. These drops are actually absorbed pretty quickly by underwear.
There is absolutely no medical or health reason to recommend either shaving, trimming or natural hair growth. It is a personal choice that should be made by every woman herself for a variety of reasons. All three ways have both positives and negatives.
The females of the human species seems to have survived largely without any problems from creation until today, shaved or not. They will continue to survive until the day our sun explodes billions and billions of years into the future.