Why didn't Hermione help Dobby when his life was in danger?

In Harry Potter and the Deathly Hallows – Part 1, we see Bellatrix throw a dagger after Dobby saved Harry and co., and in the aftermath we see Harry begging Hermione to give him anything that could save Dobby, but Hermione standing still.

Why is this? Is it too late for anything to be done? Is it because Dobby is not a human? We have definitely seen Hermione heal Ron before.

Best Answer

Several things explaining why she wasn't able to heal Dobby

Even though she had a general knowledge of various spells, she was not trained for healing - even in the books she mentions she never attempted to further her knowledge of healing wounds. Hermione knows how to use healing potions, but she isn't Madam Pomfrey. Similarly, she was not able to save Snape in deathly hallows part 2.
Hermione was definitely in shock, because she was tortured by Bellatrix several minutes ago - she needed help herself first
Dittany heals a lot of things, but a knife through the chest may not be one of them. Also as Hermione mentions, it may the injuries make even worse

" 'It's all I feel safe doing,' said Hermione shakily. 'There are spells that would put him completely right, but I daren't try in case I do them wrong and cause more damage.... He's lost so much blood already...."
Most important - she was not there while Dobby was dying at the beach, they went to house together with Ron (she is present just in the film)
Here is the list of all known healing spells. None of them can probably heal such a fatal injury Dobby has suffered.
In the book Hermione stuffed the beaded bag in her sock to save it. In the film, the snatchers got the beaded bag.