Honestly, Hermione knew Dobby was a lost case...nothing could have revived Dobby after the attack or she would have definitely helped Harry with Dobby considering she was the girl who started S.P.E.W(Society for the Elfish welfare) and fought for elf rights.

That organization didn't appear in the movies

What about dittany. It helped repair rons arm when it was almost completely separated, and maybe it could have some the same effect on dobby’s wound.

Think about if you got stabbed in the chest and were about to die. Would you rather them let you be or try and fix it and you still die?

She didn't have any dittany left she used the last of it on Ron Hermione mentioned this to Harry because he asked her about it