I don't see Light as being right for a cleric of Shar.
This.
I don't know her ability scores, but if anything, I might respec that, so she can go Trickery / Thief for her ultimate shadow spy infiltration shenanigans. Extra Bonus action on a Cleric? Yes please. In that case, she doesn't really need high Wis, her spells don't get saves; they're jsut there to augment her tricksy stuff and the odd heal. Might even go Trickery / Gloom - Gloom isn't thematically accurate, but mechanically very much so.
I really suspect her to be a former cleric of Selune; whether she knows this or not. On her own run - which might actually be my first one, Shadowheart is really my favorite out of the Origins - I'm hoping to get her to the light. However that plays out, I might respec her into something other than Trickery, not dual class her etc.