I never really understood the uproar over the Fen'Harel was Mythal's lover theory. First off - Flemeth is not Mythal. She is a human woman, only the most recent in a long line of human women, who carries a piece of Mythal's spirit in her. It's not like Flemeth would literally be his ex - if she were, her mother, grandmother, and so on would also be his exes.
...
So when I put it like that is it is kind of, um, awkward and gross

I mean, you can add Morrigan to the list for added fun! But still, not the same person, and anyway that was, what, 6000 years ago? I mean, I get that they're still friends and all, but I'm thinking they've moved on. I mean, are you bothered by the idea that the people you date in real life have had relationships, even people they loved, before you?
Anyway, they may have been lovers and it would make sense as to why Mythal would have been drawn to the original Flemeth. But I did see her relationship to Solas as a motherly one. Especially since the way they come together in that scene reminds me if that story about one of Mythal's sons... I forget which, or what the context is, but he approaches her, upset, and she reaches out to comfort him. Again, don't remember the story, and I'm on my phone so I can't look it up easily, but the image stuck with me as similar.