well we do have sort of an idiomatic thing for this, "the thing is that" => "But the thing is that I know very well (that) you speak excellent English."
"the point is that" or 'the issue is that' or 'the concern is that' similar.
The way the addition of н is taught in grammar books, is that н is added for her(him, them ...) but not for the possessive (her his their). So I have a question about this. By textbook: «случилось у её дома», is this wrong? Seeing «случилось у неё дома» makes me think of a different meaning.
Likewise, we can see «у них дома» and «у их дома» in internet search. And for его.