Look, I can see why this is confusing, but I promise you, it didn't change at lunch. If that's how she feels the next day, she felt that way all along.

Many women (my younger self included) will try very hard to make a man feel comfortable while they are face to face, even if she doesn't feel comfortable, finds him creepy, and wants to get away.

There are a few reasons women do this:

1. She genuinely just doesn't want him to feel bad. It sucks to see someone's face crumple if you shut them down. She wants to be nice to him even if he's being creepy, and she wants to get out of the situation without it being awkward. Now, because I'm older, I'm more likely to just tell a guy, "Hey, sorry, I'm not interested." But when I was young, I felt so bad - I didn't want the guy to lose confidence. I would think, "I want him to feel like women like him, and I want him to be able to find what he's looking for, but it can't be with me." So I would try to make that interaction as nice as possible, and figure out a way to let him down gently later. This is a weakness - it would be better to just tell him in the moment, to his face.

2. She's afraid he'll be mean to her or call her a bitch if she's not super nice to his face, so she's nice to him, and hopes he'll get the hint that she's not interested.

3. she's genuinely scared that the guy will hurt her if she rejects him outright. Even if they're in a public place and he won't hurt her right then, he might follow her, find out where she lives, and hurt her later. This is unlikely, and she knows it, but the fear is always there. Some guys act crazy when they're rejected.

It all comes down to being able to really read other people. Youv'e got to pay attention to nuance, not just take what they say at face value. If you ask someone out, and they say "maybe another time" without suggesting what day/time, just say, "cool, call me when you want to hang out." Make sure she knows the ball is in her court, then LEAVE HER ALONE. She'll call if she's interested.