This is a different question, but related. I've been thinking about why Bianca might resurface during the game. The obvious possibility is Varric going after her, but he's had ten years and apparently hasn't found her yet, for whatever reason. I've been wondering if Bianca might come to us, to get help from either Varric or the Inquisition.
One of my theories is that the Carta (whom I really think was the cause of her and Varric's split) has gotten a hold of red lyrium. Here's what I'm thinking:
Once the division of the Templar Order was done, and (what is now known as) the Red Templars were established, the splinter group faced a serious problem. Without access to the Chantry's supplies, they were going to be out of lyrium soon. Even with legal contacts they made on the side, it was probably only a matter of time before the Loyal Templars would find them.
It's possible that they might have heard of exactly what happened to KC Meredith, and how she became very powerful before she died. Thanks to some red lyrium that the Champion had found. In my mind, these guys have quite the hubris. They probably figured that they could master the red lyrium for themselves. Trying to take notes from Meredith's downfall, they find a sample and begin to experiment. I could imagine that some of those experiments were brutal, and often fatal.
About that time, the Carta manages to find the Thaig were the red lyrium idol was first discovered all those years ago. Gazing upon the crystalline structures of red lyrium, the dwarves didn't see the danger. They saw opportunity. Word has probably spread that the Templar order had split, and that surely the rebels were going to need lyrium, right? The timing couldn't have been better.
The Red Templars, facing a lack of fresh red lyrium as well as running low on blue, decided to finally go to the one group that Chantry wouldn't have spies or sympathizers in: The Carta. Paying an exorbitant sum, the Red Templars set up a smuggling deal with the Carta to go more of the powerful new lyrium.
Now time has passed, and the Red Templars have their new power. Yet, there is a catch. More and more members of the Carta are reporting symptoms of madness, confusion, mood swings...and mentions of a song. The most beautiful song anyone has ever heard. Trade is not only in danger of being disrupted, but the Carta are starting to lose themselves to the song of the red lyrium.
Bianca has been with the Carta for over ten years now. Seeing the writing on the wall, she quietly packs and flees, seeking to get away as fast as she could. Hoping to find help from her contacts still in the Merchant's Guild, she ends up facing the last ghost of her past: Varric. The man that still filled her heart with regret. The man that told her his principles were worth more than any riches. The man that she tried to forget, her first love.
Will her laugh at her misfortune now? Has he changed so much that he would turn his back on a old friend? She wouldn't have blamed him, but she had to try. Her life, and the life of her friends, depended upon it.
Wow, that was wordy. Sorry about that. 