When a woman says "I miss you," she's signaling real attachment. The phrase means you matter enough that your absence creates a genuine loss for her, whether it's about a recent event or something further back.
The second thing women will say that reveal that they have feelings for you is, "Oh, I missed you," or, "I miss you." Let's say, for example, you were supposed to go to some kind of event that she was going to as well, but you weren't there. And she says, "Hey, I missed you." This clearly shows that in the evening there was a hole, a hole that you were supposed to fill, but you weren't there and she felt that loss. You clearly matter to her. The same is true if maybe she hasn't seen you for a while, or maybe she's seen you very recently, and she says something like, "Hey, I miss you!" She's letting you know, "You matter to me."
