The way a woman reacts after sex comes down to two things:
1) How she is used to and where she wants to take this relation + what kinda feeling the sex gave her. There are women who are sluts and are only in it for the ride. There are women who are not sluts but they don't want a relationship right or any kind of very close feelings. Then there are women who didn't like the sex and do not expect them to be so close to you anyways after it.
2) The vibe you give as a man and the way you approach them up to the point of sex. Some guys are just weirdos and cool and everything and they will give off a vibe of only wanting to have sex so do not expect her to be so open about hugging you and cuddling you. Some men approach women sweetly, in a charming way that makes them wanna fall in love LOL
But as
@deesade wrote above, women release oxytocin after orgasm and that is also known as the bonding hormone so usually, they want to bond after it. It is part of primal behaviour where the woman wants to feel security in the person she possibly will have children with, she wants to feel he will stay around and take care of things. Of course this is only primal behaviour, but this is why it happens basically.