Just Friends?

I posed this question on a writer's forum a while back about a novel idea involving a rewrite from a fandom plot. (Which fandom isn't relevant, as completely restructuring the world from the ground up would be part of my game plan.) I thought it would be fun to ask it of my blog, especially as there are some new folks following me now (Hi!).

Here's the scenario - I've provided the names for ease ...

Kailyst and Imori have known each other for approaching two decades, as close friends and business partners (actually, criminal partners - they're the villains). They met when he was twelve, she was fifteen. There is no romantic vibe between the two.

In this potential scenario, Kailyst falls in love with Seshanna and gets married. Imori is no fan from the beginning (personality clashes), but after some months, she raises concerns that Seshanna is interfering with Kailyst's judgment on the business side. Now, two things are relevant: a) being they're partners, this affects Imori's success as well; and b) she's right - his wife's presence *is* hindering him. When being vocal doesn't work, she gets nasty.

Now here's my dilemma: I need / want to keep it unequivocal that there's no romantic motivation, hidden or obvious, in Imori's actions against Seshanna. Probably some jealousy is inevitable, but the overall vibe should be platonic.

So I wondered if which scenario would make this more plausible:

A) There's never been any hint of attraction between Kailyst and Imori. The question has never been on either of their radars.
B) Probably when one or the other was in their late teens (that is, after they'd known each other for years, but still about / over a decade ago), they experimented, kissed, whatever, and the immediate, mutual reaction was, "Eww. No. We must never speak of this again."

That's the question, then after a ridiculous amount of setup: A or B?

There's also C, I suppose, which is come up with a supernatural / magical reason why Imori's not even capable of going there, but that feels a bit like cheating. (Let's not mention that building the world around the plot is completely the opposite of the way I usually work, so it feels darn weird.)

As a point of interest, when I posed this on the writer's forum, B had a slight majority. More interestingly, if depressingly cliche, most of the men who responded had trouble believing that such a relation could have been consistently platonic; most of the women thought it seemed plausible. (Since it's her-to-him I'm concerned about, not him-to-her - he's pretty rabidly devoted to his wife - I can live with this reaction in any case.)

Thanks, anyone who feels like putting in their two cents. I am just insufferably nosey, and just as interested in how people view this as actually solving the problem. ;-)