I'm a guy, but I've gotten feedback from girls, so I can offer some answer.
Girth > Length.
Of course length matters, but only by 4 inches is needed to reach her sensitive areas, if you have more than 4 inches, that's great. But what really counts is the girth and thickness of your member. If you don't have girth, then your soldier ain't worth spit, even if it were 10 inches.