I believe that T-Pol was Chaste when she mated with Trip as she Bonded with him.
If she had mated with Phlox she would have bonded with him and could not have Bonded with Trip.
Or at least that is the way I see it.
I am not an authority on the matter, but isn't the bonding the result of repeated contact?
(I don't mean just sex but also psychological intimacy.) Anyway, that 'bonding' is the Vulcan equivalent of infatuation. I believe that there are chemical changes in humans, too, when we are in love. Maybe not neurological, though, (or not that much) because we're not telepaths. Which suggests that T'Pol wouldn't have a bonding with Dr Phlox because he only helped her (in person or not) with her physiological needs. Or am I completely missing the point that Pon Farr is essentially a neurological imbalance? Still, I don't want to believe that a Vulcan bonding would surge from a single intercourse.