Yes, because Sarafine left Lena and John (Lena's dad, not John Breed, haha) to die when Lena was a baby. I would've done the same if I was Lena Duchannes.
Yes, I think it was fair. Not just because she caused Lena's dad's death and tried to kill Lena. If you think about it Lena's mom had the choice to decide to join Abraham , and she did. She deserves what she got. Even though i still like her. Also if you think about it the last line Sarafine said to Lena's father was " I'll love until the day after forever." Sarafine also said that to Lena before she she was engulfed in the flames. So if you think about Sarafine would have probably killed Lena in the end.