I genuinely think there was/is a little somethin-somethin going on. There was just so much smoke for there not to be a bit of fire. But relationships have so many different levels that it's hard to tell what the somethin-somethin was.
Given their geographical distance - and his work schedule - a FWB scenario seems a possibility: we're on the same continent, there's a kitchen door close by, we go for it!! But neither needs to stick around if it doesn't fit into a personal schedule - hence her leaving less than a week after date night.
Mind you, if it came out that they were just friends - no benefits - that wouldn't surprise me either.