I tend to agree. She has a fairly distinct personality, though I suppose it's technically possible that the entity we're calling 'Deirdre' actually is a particular Fallen playing the role. I really doubt that, though.
I'd say she was born, raised, and carefully groomed to be what she is by Nicodemus and Tessa, probably especially the former, Tessa seems more like she'd be off doing her own semi-random thing at any given time. Deirdre definitely seems fonder of her father (too fond, some would say) than she does of Tessa.
Here's an interestingly ghastly possibility that would fit Nicodemus and Tessa all too well: suppose they've had a bunch of kids, letting them compete for the 'honor' of a Coin, and offed the failures?
Nic seems to actually be nice to Deirdre and care about her (whether this is wholly or partially self interest to have a powerful and loyal assistant or true caring I don't know). Tessa seems to think more short term and not treat her daughter with caring.