I actually picked up a cute girl last night at the club, who during grind dancing with me said "I don't usually let guys touch me!!!!". This morning after we had sex multiple times, she said again "Don't get your hopes up. I don't usually do this!"
You'll often here variations of this statement: "I don't EVER do this!", "Don't get any ideas...I don't sleep with guys the first date", etc etc.
What this means is 3-fold:
1) She is thinking of doing whatever she is denying
What does it mean if your friend says "I'm not going to buy that car today...just FYI!"? It means your friend is seriously considering buying a car. Normal people who aren't in the market for a car don't say things like this.
Likewise, normal girls who don't have ONS or casual sex in their character don't feel the need to proclaim "by the way, I don't do casual sex!". Because it's a given for them.
So this is just a form of "denial". She's actually convincing herself not to do it.
2) But she is also trying to convince YOU as well (shit-test).
This is where you come in. Woe be to all betas.
By being confrontational and challenging you directly, she is shit-testing you. She is assessing your evolutionary fitness. If you are beta, you back down and "respect" her wishes. If you are alpha, you demonstrate your SMV and are capable of changing what her "wishes" are in the first place.
Women don't get "fucks" from betas, so this test is crucial for them to weed out guys who don't have the resolve to push through Last Minute Resistance or 2nd Date Resistance. Remember, this is for females' benefit and it's key to understand why they do this.
3) Hypoagency. Plausiable deniability if she does have sex with you
Lastly, any statement like in the title serves as a way to a) uphold her chastity b) put the onus on you.
By outright stating she doesn't usually hookup quickly, she can hamster away sex by saying it was because of YOU. Not her decision. She's still a good girl and doesn't do this. It doesn't count. It's just one time. Sex doesn't tell anything about her as a person.
It's a No True Scotsman applied to the self: "I don't EVER do X...except when I do X. But those times weren't TRUE Xs!"
EDIT: TL;DR Women have lots of mechanisms to a) inflate the value/cost of their sex b) maintain their self-derived notion they are chaste c) abdicate agency to men, so anything they do cannot be their fault.
Add your own response to this shit-test.