A male dog will lick his penis. A female dog will lick her vulva. And they will both lick their anal regions. This less than appealing behavior annoys pet owners.
If we see that the vulva of the bitch is for your dog licking her genital area.
This guide will help you determine if your dog's vagina is healthy or if you need Discharge from the vulva, which may contain pus or blood; Licking at the vulva.