Question: Why Does My Female Dog Mount Other Dogs?
Answer: It's not what you think, although the sight of a female dog (or even a neutered male) mounting the back of another dog (of any gender) can be a tad shocking.
Mounting is not necessarily about sex when it comes to dogs. In most cases (neutered males and females) this behaviour is a dominance play, meant to force the other dog into submission. It is also just play, no deeper meaning to it at all. A more dominant dog may use this frequently to establish himself as higher in the heirarchy, but between dogs who have their pack position well-sorted, it is just a wrestling move, and a brief stint on the top will not elevate a lower-ranking dog to a higher position unless a challenge is clearly won.