Board Thread:Question and Answer/@comment-125.164.14.236-20141120135128/@comment-25560888-20141124063200

the purpose of likability meter is the specific "ENCOUNTER" wherein you made the likability meter full (4 hearts), you'll get that card's drop 100% guaranteed (highlighted with pink in the Finish tab)...

as for increasing the likability meter, just encountering the card is sufficient to randomly increase it... you dont have to kill it by yourself...

@original post: you just got unlucky... just encounter her more and it will increase eventually ^_^

@1st comment: that drop @lvl68 Vitruvius is a lucky one... you'll get one more drop 100% sure if you fill 2 more hearts ^_^