In Dark series Season 3, we see that Hannah travels back to 1911, to Adam (Jonas, his son) alongside Silja who is his half-sister. Adam tells them that they are in "wrong place". So at midnight, Adam sneaks into Hannah and Silja's room to take Silja and send her to post-apocalypse time. But Hannah wakes up and after a little chat with Adam (which is not aggressive), Adam suffocates and kills her, his mother!
Was it necessary to kill her? Although she is secretly a cunning, selfish and ruthless individual, she happens to care about Jonas and throughout the story we don't see a clue that Jonas is upset about her actions. Jonas is a powerful man in 1911 and definitely Hannah can't stop him to do his job.