I remember (a very long time ago) being struck by the character of Michal, who appears in the background at various points of David's story, and going through the relevant sections of the Bible gleaning all the references to her, with the idea of making a coherent character arc out of it. (This was before online searchable versions, obviously...)

But I wouldn't have made her fall out of love with David because he agrees to pay a bride-price which she thinks barbaric, because that is (a) non-canon and (b) sounds like a very modern (and hence anachronistic) attitude.