Hmm. Is this a series romance? Or just a one-off that happens to be a romance? Or is it more of a literary novel? Cause I think that genre conventions would definitely come into play here, particularly if the publisher has a romance "line" it fits into.

As for the triangle, I don't even see it as much of a triangle, because she's not honestly torn between the two men by your description: she's torn between her love and her vows. I can respect honest triangles, where both men are portrayed fairly and it's a believable, realistic conflict. This sort of thing stacks the deck, though, and the end is somewhat foregone if the husband is an outright asshole.