If she just wants casual sex, by all means... Or if they've been friends for a long time and just happened to go on a first date...
Actually I think many men also aren't looking for sex on the first date. Fortunately.
Personally, I also think that quality men who I would eventually like to get into a serious relationship with, are not only not looking for sex on the first date, also not the second nor the third: because guys who actually like you take their time to get to know you better and don't want to spook you. And smart people usually don't go around sharing their body with just anyone without knowing where they've been... but that's just my opinion.
It depends. My friend did that once and I was like why? But the worst part was this guy was freaking PAYING WITH A BAG OF PENNIES!!! A legit bag of pennies. When I found out she slept with him I told her off. I couldn't believe she would do something like that. I literally was so disappointed with her. Like he didn't deserve anything. Like that's as low as you get. She should've left when she saw him with that freaking bag of pennies. So embarrassing.
I just want to say that if a woman has sex on the first date, she's giving something to him that is make it or break it. If you have sex on the first date and it's "not good", they're gone. If someone has sex on the first date and loves it, that's all they're staying for so they're just going to leave you once they lose interest or just find another target. Draw your own conclusions
It's rare to meet a girl who is 100% consistent. It's hard to find a girl who always has sex on the first date but it's also rare to meet a girl who never has sex on the first date.
So even if she makes YOU wait 3 months for sex, chances are high that she's had sex with at least 1 or 2 other guys way sooner than she had sex with you.
However if she sleeps with you right away that means you were one of the guys who she was most excited to sleep with so I think it's dumb to lose interest in a girl who wants to sleep with you. It should be considered a good thing.