Originating from the webcomic Waspi Square, Tina is a collective of personal demons inhabiting a soul-less human body. Because of the personal demon status, "Tina" is not allowed to harm any other humans with words or advice - something that makes working at Coffee of Doom much more awkward. During her introduction on Twisted it was revealed that she was one of the many "innocents" which Señior Diablo fought against Twisted's original Council to free from Hell.
Tina has the ability to read people's problems from their auras and metaphorical baggage and uses her position in the coffee shop to offer helpful advice to people who come in while she's working as well as have exactly the right beverage made for the customer before they ask.
Now if only she could do something about Coffee of Doom's "attitude" problem.