In the Deathly Hallows part 2, Harry is looking into Snape's memories and he sees Snape talking to
Dumbledore asking him about Harry,
and Snape sends his Patronus to go help Harry find the sword of Gryffindor (Deathly Hallows Part 1). How is Snape talking to
Dumbledore, because this conversation takes place after Dumbledore was killed?
Snape was talking to Dumbledore's headmaster portrait, at least in the book:
‘Headmaster! They are camping in the Forest of Dean! The Mudblood –’
‘Do not use that word!’
‘– the Granger girl, then, mentioned the place as she opened her bag and I heard her!’
‘Good. Very good!’ cried the portrait of Dumbledore behind the Headmaster’s chair. ‘Now, Severus, the sword! Do not forget that it must be taken under conditions of need and valour – and he must not know that you give it! If Voldemort should read Harry’s mind and see you acting for him –’
‘I know,’ said Snape curtly. He approached the portrait of Dumbledore and pulled at its side. It swung forwards, revealing a hidden cavity behind it, from which he took the sword of Gryffindor. Deathly Hallows
