I had experience with this last weekend. What i did was pretty similar as i kept asking and being persistant but all the time being cool about it.

My frame was 'i want you to come back to spend some more time together, i understand you're scared of looking like a slag to your mates but i don't know when we'll see eachother again.' I really believe she could sense this.

I even went as far as verbalising it, "If you don't wanna come and chill i understand, no worries, probably see you up here soon again anyway" I must have said this, or similar statement, 3 or 4 times. Needless to say, she came and 'chilled'.

The mindset of DESIRE/INTENT without ATTACHMENT is the key.

I understand this would be difficult if the girl is your proper type (this one was HB7.5 so probably made it easier) and it depends on the individual, but it has worked for me.

The way i see it, i'm not shagging them as it stands so i might aswell go for the close.