Getting over someone is hard. I prefer not to phrase it as: "she's just another girl" because that diminishes the fact that to you she was special and more than "just another girl". That's why you have these feelings of attraction & desire in the first place.
But, her being special doesn't mean she's someone you'll end up with in a long relationship. Your attraction & affection for her is only half a relationship. There will be MANY women (or men, it goes both ways) you meet in life that seem amazing & special, but don't return those feelings towards you. And I don't mean this as a downer; it's just a reality... It doesn't mean there's something wrong with you because you're not the type of person a specific girl is interested in dating.
It's not about getting over her; as hard as that is to hear it means there's not a relationship there. It takes both people for a relationship to form (a healthy one at least, which I hope is what you're after). It sucks, but it happens. You have to learn to move past that and continue living your life (including meeting other people & potential partners). You're not getting over "her"; you're getting over a relationship that you'd like to exist but doesn't.
I'll not make light of how hard it can be to move past someone, as I see some others do in their replies. Attraction for someone should take time to get over. It's hard to experience a strong amount of attraction towards someone and not have that returned. But the reality is there will probably be many people in your life that fit this description. Don't dwell on the people who aren't returning your affection; and figure out what you need to do to redirect that energy into finding someone for whom the attraction is mutual. Because that's when you'll eventually find someone who really is special; as hard as it might seem now to think of someone being more special than this current girl... odds are it will happen. Then you'll get to have a whole relationship with them (rather than a one-sided one). And being in a mutual relationship will be far better than what you're longing for now.
Source: mid-forties and have gone through many break-ups and a divorce. When a relationship isn't working out, figure out what you need to do to move past it & look for the next one.