I just don't understand why they brought her in at all. They had a great opportunity to leave her out of both the comics and the game which would leave us always with that wonderful mystery of who really stole Varric's heart. Not everything that is mentioned needs to be revealed in game. Some things can remain unanswered and forever illusive. Bianca was a perfect example of this. She's much more appealing as a great unknown love of Varric's than she could ever be when given life. The Bianca we were presented with is proof of this fact.
They obviously needed to make her a Dwarven mechanical genius, seeing as though no-one else seems to be able to figure out a reloading crossbow at that time. Then they must have thought that for Varric to hold such love for her, she would need to be several levels above him in most regards. Smarter. Wittier. More confident. A better shot. Revered by her peers etc. Then they needed to create conflict between these star-crossed lovers. Cause you know, big hole in the sky, everyone is going to die just isn't enough for one Dwarf. Altogether, we're just left with an unsatisfying story based mission and an underwhelming character reveal.