Quickly and desperately.

You rapidly realize if you stay there any longer she will trap you with her sexual skills. She knows how to manipulate you and even if she didn't would quickly figure it out if given the time. As Fiona drops her ass and body down you finish pulling your underwear and pants up knocking her off-balance in the small empty changing room stall. She yelps in surprise and manages to catch herself from hitting the ground hard. You take the opportunity to jet from the stall. Trying to act normal with the few patrons in the department store you fast walk out. On the way grabbing a spritz of cologne to cover up whatever scent Fiona may have left on you. Jetting to your car you make it to church on time though not enough time to change your cloths. Equipped with a massive hard-on you are trying to hide the whole time you meet Sarah at church and go though the sermon. You miraculously managed to preserve your engagement through the first full day. But you know that like a shark Fiona smells blood and will be more aggressive from here on out.