She could have been a blood bag to the family and due to Alec's protective kindness, fallen in love with him at an early age. It only grew as she did but he never aged.

His kindness to her was part of the reason Vlad chose her.

Prior to that Vlad dished out ever cruelty imaginable to Alek's lover when he wasn't present, and while she never let tell of it, he had the haunting sickening suspicions. 

Sabine might have briefly known her but not known of 'them'.


And thanks btw XD