Try not to worry. Your baby doesn't have a lack of boy parts or three generic lines, she has obvious girl parts. I sympathize completely with the annoyance and stress of all the people wanting to tell you horror stories, believe me, but most of them just don't get that there are one or two right ways to ID girls and quite a few more wrong ways. That doesn't mean that no girl prediction can ever be 100% accurate.
I can't speak from some vast well of professional experience, but strictly based on my time here I can't think of one incorrect gender prediction of a physically typical baby that couldn't be directly attributed to some form of operator error. Not one. (Many are so obvious that we can spot them from still images before they're ever even confirmed.) Sometimes the view is poor and the person scanning makes a guess that turns out to be wrong; other times the baby has its legs spread wide and they just misinterpret what they're looking at. Occasionally they're so utterly inexcusable that they make me want to bang my head on my desk until my eyes bleed.
I'm not saying it's never happened that some highly trained, highly experienced sonographer went through an entire scan seeing only perfect shots that looked exactly like one gender on a baby that was actually of the opposite gender (and had no physical issues), but if it has I've never heard about it or seen it. I'm not even sure how something like that would happen.