Like them above said.. relax, not a problem.
It doesn't have to be all about the fucking if you don't want it to be. Plenty of other things to do before and after. Enjoy them.
If you really think it's going to happen sooner than you want and you won't get it up again, just arrange things with the girl to fuck last, and tell her.
As a certified two-pump-chump by my own admission, that's what I do..
She's not your girlfriend, she won't know what you're like, and what you want, so open your mouth before she puts your dick in hers, to make sure it goes how you want.
As always, your mileage may vary.