When Jay showed Gal his automatic rifle he told Gal that Shel had bought it for him. She was also quite proficient with guns as indicated near the end. Was this supposed to indicate she had some connection with Jay's occupation?
shareI just assumed he taught her those things (or at least brought her to a shooting range) at some point in their relationship in the case of an emergency like what happened near the end.
shareWhen Fiona and Gal are over for the dinner party Fiona points to the picture of Shel in a military uniform and Shel talks about how she willingly joined the Swedish Military. So I assume that's supposed to explain her weapon proficiency, as well she seems to have very open knowledge of Jays profession from the get-go and doesn't really seem to mind at all so she's probably comfortable, at least in some sense, with killing and guns and whatnot.