There are some good points being made here. I accept that Shadowheart's high Dex is fitting... although I don't think that makes her better on the front line, not at all. Two people mentioned that as if it's definitionally true, and I disagree.
What do you base that on?
It comes down to very simple math. +1AC from higher Dex is the most important stat for a frontliner here. With a finesse weapon she has the same attack bonus and only 1 point of damage less than she would have with 14 Str and a mace. 1 point of AC > 1 point of damage, by a wide margin.
AC is king in combat.