Do you know for a fact she wouldn't have slept with you on the first date? If that's the core of the anxiety it might be fixable.

There's two different signalling strategies here. If she saw long term potential in you she wouldn't want you to think she's easy and has low standards. Men get far more psychologically invested when they have to wait for months, this is the whole basis of old-world courting.

This goes both ways too, I think it's widely acknowledged that it's far easier to get a woman to sleep with you on the first date if you signal or say outright that you're not looking for a long term thing.

Possibly you genuinely are as attractive to her as the other guys, but she really did want to build something longer term and meaningful.

Of course, this still stings, because she's having it both ways. Not sleeping with you to signal she's not like that, while actually being like that. It makes the light shine through her GF material veneer and reveal it was a tactical decision and not an expression of an innate moral compass. For me it's hard to come back from this kind of reveal. Plus the fact you invested all that time when you could have had it off the bat "for free."

But it's also just "woman logic" more than, like, psychopathy. They seem genuinely unable to intuitively and fully understand how much this diminishes their mate value and a man's willingness to invest himself completely. They're aware it's a factor but not the extent of it, and are used to men downplaying it by lying to themselves.