They had been dating for a couple of years at least. Although she and her ex husband were together on and off for much of their 20s. In that interview where she announced her pregnancy she did say she took the divorce as a way to evaluate what she really wanted out of life, so I hope it works out for her. He already has three teenage and down kids from a previous marriage.
She's probably not the first in the Percy family to have conception and marriage occur that way around. "premature first babies are always big and healthy for being born at 6-7 months" and all that.