First, I gotta say that some of your reactions to people's thoughts about your OP have been kinda harsh. You asked us for our thoughts, remember? No need to go off on us, maaaaaan!
Anyway... I understand the two paths of thought being expressed on here. Thought path 1 says "the fact that she brought it up means she had sex on her mind and wanted it," while thought path 2 says "the fact that she brought it up means she's an attention wh0re who was just playing mind games with him the whole time."
What's important to realize, however, is that at the time she said it there was NO real indication of which thought path she was on. Therefore, regardless of what she was thinking, the best action to counter-act either one should have been the same:
INDIFFERENCE.
In other words, there was no need for you to have a reaction whereby you're showing her you're emotionally invested in either outcome. Ironically, I have found that doing this tends to make the girl more apt to go in the route of wanting to have sex with me.
Real talk: I went out with an Armenian chick once. On our first date we saw a movie, then at the end we made out in her car. I wanted her to drive me back to my place so we could do whatever. She said she had been hurt in the past and wanted to take it slow. My reaction? "Sure, no problem."
On the second date, after we went out to eat, she drove me back to my apartment. I thought she was just going to drop me off; she asks if she can come in so we can watch a movie, and I say "Sure, no problem."
While on the couch watching the movie, we start making out heavy. Suddenly, she pulls away and says "Just so you know, we're not having sex tonight."
Now, up to this point I have not once mentioned trying to have sex with her, so I know she's thinking about it and trying to resist out of fear of being hurt. So what did I do? Did I turn all the lights back on and send her home? NO.
I simply said to her: "Look, I'm just trying to get to know you. You're the one that's brought up sex so far, not me. If it happens, great, but if not, that's fine, too - like I said, I'm just enjoying getting to know you."
3 hours later she was in my bed (which SHE decided to go to first, not me), I was kissing on her neck, she was pulling my boxers off and we were going at it like wild animals. All because I was indifferent to the outcome.
Bottom line: not all girls are 1st-date bangers; there will be girls who won't want to do it until the 2nd or 3rd date, or even longer. However, if the interest from them to bang you IS there, it's okay to wait it out a bit (and if you don't want to wait, you're welcome to find girls that won't wait either).
More importantly, though, it will be easier to make these girls feel comfortable about banging them sooner if you DON'T respond to their "not having sex" convo with actions indicating that that's all you wanted from them in the first place. Yes, she's in your room, in your bed, but that doesn't mean you've made the sale yet.
In fact, when she told you that, your best move would have been to say, "Wow, somebody's got sex on the brain, don't they?" then played with her like, "Well, that's all good. So, let's move this party to the living room, shall we?" Her guard would have been put down a bit by you moving her away from the "prime sex location" - i.e. a bed - and she probably would have ended up screwing you on your couch instead!