I wonder what registry a 300 year old vampire with a 19 year old trophy co-ed is on? Tangent to that, will the series have Laura's backstory stay with the book and her mother's family being descended from the Karnsteins. We could be looking at Vampire Dueling Banjos down the line.
Three centuries down, that connection is very distant, of course. However, it could be something that becomes part of re-appreciating Laura from Mattie. While Mattie is a sister in Death, Laura actually is family which connects Carmilla to a humanity she has thought long since lost.
In the book, there is implication that Carmilla is targeting descendants of the Karnsteins. Rather like, gathering a family she can have in death. The series has used a lot of themes from the book, inverting them into something positive, so I wonder if they might do that here. Have Carmilla learn she is not cut off from humanity because her Karnstein family does live on?