Size Comparison Update
With her human form in the mix it really helps you to visualize just how massive these things can get.

Lore wise Babette actually gets even bigger, though that is a tale for another time.

I'm not quite sure how I should approach Cosette's pre tragedy human form. She is (Was) an identical twin of Mariette, And given that it will be a sort of neutral T pose I'm half tempted to just flip Mariette's pose backwards and call it a day. XD

No no laziness is bad. 

The two will be maybe 1 - .5 heads shorter than  their mother, Babette, Though I really did like the idea that through the transformation that Babette by the end looks nearly identical to Mariette in her wolf prime. That the transformation repairing her body has made her appear to be younger than she is.

That brings to mind the idea of lifespans. Just what is the natural life span of a Werewolf? Is it basically the same as the human? If I'm using this mechanic would an old looking werewolf actually be like an ancient being hundreds of years old? Are they even capable of dieing naturally? 

They can't kill themselves, not unless they are extremely crafty about it. Since the body goes into a sort of primal instinct/berserk mode when it detects that their own consciousness has become a danger shutting it off till the body can neutralize the situation.

It would make sense though that those who are the most slapdash about abusing their powers would get pacified by external forces sooner or later.