I suspect she's heard that he's been making Gooey eyes at the likes of Rachael and Tindra and she's stormed off in a huff.
You can't afford to keep a classy piece of work like Fiona dangling on a piece of string for long.

I have some unfinished business myself with Fiona so i've whisked her away for a long weekend in exotic Clacton. This will give me a better opportunity to fully appreciate her exquisite underwear without fear of interruption, after which i can turn my attention to studying her__!!!