The point of that moment was character setting the awful businessman guy. He's so narcissistic and utterly disinterested in the people ferreting around on his behalf that he was unaware who the wife of his niece even was. Next thing, he sacks the manager of his new hotel like swatting a fly. It seemed natural because we'd built his personality very quickly.
Replace the sentence Frankie said with: "I love puppies.", or "But I'm not related to you.". It wouldn't make sense and take you out of the scene for the former, and for the latter, it would make more sense and wouldn't take you out of the scene much. But it would still make the businessman an awful person in either case as that is established afterwards from actions, not something that may have been offscreen between Frankie and the businessman prior to the start of the episode. Therefore, the original sentence served no in story purpose other than to have that sentence in that scene to stand out.
I love swimming, especially in bright sunshine yellow socks, even though I don't do it often.
^
Pointless sentence above.
Her sexuality was incidental and obsessing over the sexual leanings of a minor character isn't them rubbing your face in it - it's you getting sidetracked by your own bigotry.
Wow, MY bigotry? Not YOUR bigotry to people like me who are raising things which aren't even sexuality based as the actual problem? Again, I've already said that it's not her sexuality that's the problem, but it's part of what's so jarring about it all. It's the pointlessness of the sentence which means it's not being used for anything other than for the writers to put that message out to the audience.
Again, Captain Jack? No issue. His sexuality wasn't highlighted or anything. It just was. Ianto Jones? It wasn't highlighted in the episode he appeared in either. So I have issue with one but not the other? Really?
The issue is the writers who are putting these in willy-nilly and it becomes very jarring to some viewers. Something which should be intergrated well into the story (again, check out Captain Jack Harkness), instead becomes a break in the whole scene, and anything that is done then is VERY noticable. And it has been done twice so far out of four episodes, it's become VERY noticable.
Episode 2, Planet Desolation, the Female alien comments that her wife is dead too. Not an issue content wise, but the way it was done was not. No hint of marriage or relationship, then we come out with it and it's just so she can say it's "her wife" that's been killed too. But that one at least was part of the story (not very well, but at least it tried). And now in Episode 4, right at the start, we get a "Who are you?" which begs people to pay attention, and we get a "I'm married to your niece.". So it's very clearly designed to be put front and centre. (But again, as it could easily have not been included and it wouldn't have changed a thing, it's clearly an intended message).
Which means either the writers are REALLY bad (which is very likely at the moment I'd say), or they are deliberately trying very hard to integrating these parts in to push their messages across.