Firstly, this happens to everyone, even experienced guys, where they run out of things to say. We all get in our head sometimes. We're human, and it happens to men and women. It's every guys' biggest fear. It's the one fear that stops us from going and having a conversation (that, and rejection). Here is my tip for anyone on how to move past it:
If you really can't come up with ANY possible convo topic (cuz ur in your head probably), admit it, but be playful about it. It actually works because you're acknowledging something that happens to EVERYBODY! And it shows your human side. You neutralize the awkwardness by acknowledging it. Get it? An example is to be like "Yeah, I can't think of anything to say, so let's stand here and just gaze into each other's eyes"
Another one I like is " *silence for a few seconds* ... Oh, I'm I gonna have to do all the talking? Geez"
Again, these are done playfully. The key tho, is to be comfortable with the silence. If you're awkward, the nervous energy will make her nervous (law of state transfer [trust me, I'm an engineer]). If you're comfortable with it, like it's no big deal, and maintaining eye contact, you'll come off as confident