Part of me feels not pushing a little more that night is what made her feel there wasn't "chemistry."

Before I get to your quote, I want to say that she said she isn't feeling it so that's that. You need to try and move on. You can't keep trying to force something when you've been told no. Also, it's possible she didn't have quite as good a time with you as you did. Also, it's possible she had a good time but recently met a guy she likes a bit more than you. Hey it happens.

That said, and back to your quote...

I've felt that same thing before. As a guy you have to be very observant and you have to try to intuit how she's feeling about things. Every woman is different, of course, as some appreciate it when a guy moves a bit slower where others might take some level of offense.

It can be tougher when you are trying to take things slow out of respect as there are situations where if you don't escalate in some way she may interpret it as a lack of interest in your part which could trigger a reciprocal lack of interest on her part. So even if you don't think pushing for sex is a great idea, some form of escalation and showing interest on your part (I mean, you're on a romantic date after all) is usually a good thing.