In Euripides' Medea, how is Medea a victim of the gods or where and when is Medea cursed by the gods?
This question strikes me as rather challenging, since I probably would not consider her a victim of the gods nor would I consider her as being cursed by the gods.
Later in the play, Medea will have been assisted by the goddess Hecate in the creation of the clothing that destroys Creon's daughter. Also, at the end of the play, she is even assisted by the gods as she uses the chariot of the sun god Helios to escape from Corinth.
Perhaps, in the mythic tradition surrounding the story, Medea could be considered a pawn of the gods, namely Hera, who uses Medea to bring destruction upon Pelias, whom Hera hated because he did not honor her appropriately. I do not recall, however, that Euripides brings this before the audience for consideration.
At one point, Jason suggests that Aphrodite was responsible for the success of his journey, so, perhaps, we could say that Medea suffers at the hands of Aphrodite.
I consider goddess Aphrodite
the only one of gods or mortal men
who saved my expedition. As for you,
well, you've a subtle mind. But if I told
how Eros with his unerring arrows
forced you to save me, I could injure you.
(Ian Johnston translation)