Personally I would say she's already made up in her mind whether she's going to fuck you or not, thought the chances are good if she's agreed to come round to yours for the evening, I would however point out 2 things.

Firstly you have dated her 18months ago and then again recently. She already has a perception of you. You can just switch all "pua tactics" on for 1 date as your behaviour will come across as erratic unless you are incrrdeibly confident.

Secondly and more generally girls who pay for dating websites such as eharmony and match.com are less likely to want to sleep around. As the websites are subscription based and you have to pay a decent sum of money, most girls on there will be looking for something a little more serious whereas Plenty of Fish has the slags. That's personally what i've found...