In Harry Potter 7 (I), Dobby was finally stabbed, but why didn't Hermione save Dobby?

In Harry Potter 7- I, Hermione was not saved, but it was too late to be saved.

In the original book, Hermione was in a semi-coma when she was rescued to the shell hut. When she woke up, Dobby was dead.

Dobby arrived at Malfoy Manor after receiving the news of Aberforth in the seventh film (Harry Potter and the Deathly Hallows). Bellatrix stabbed Harry, Ron, Hermione and others in the chest with a silver knife and died tragically (see Chapter 23 of Harry Potter and the Deathly Hallows).

After his death, Harry Potter personally dug up the ground and buried it near Furong's shell hut with the inscription: "Dobby, a free elf, sleeps here."

Extended data:

Dobby made his debut in Harry Potter and the Chamber of Secrets, warning Harry of possible dangers and preventing him from going to Hogwarts. After winning the decisive battle with tom riddle in the secret room, Harry came to Dumbledore's office; Lucius malfoy also came, because he wanted to know the outcome of the decisive battle.

After he left, Harry put his socks in Tom's diary and gave them to Lucius. Because they belonged to Voldemort, Lucius took them and gave them to Dobby. In this way, the master Lucius gave Dobby a sock, and Dobby became a free elf (when the house elf took the clothes from the master, it meant freedom).

Later, Dobby looked around for a job, but he was always rejected because he asked for money as a house elf. After that, with Dumbledore's permission, he and Spock worked together in Hogwarts kitchen, one Galen a week and one day off in January.