I assume from trying to understand the title that this probably has something to do with time travel. Maybe the woman can only time warp for a specific amount of time indicated by the watch ?
Just a theory though
It's almost for sure a time travel thing. I'm guessing she's going backwards so while from his perspective this is their first meeting, for her it's their last.
@Brightamethyst Ah right, I focused too much on how she should know when they would meet again, didn't consider that for her all of this was akin to him dying. (Unless she can spring some "forgotten childhood friend" shenanigans, but that'd still just be like methadone)