There's a flicker of incredulity in Rita's expression when Strange mentions a 'prophecy', but he moves on before she can question him about it.

Well, she can't blame him for wanting to know what happened while he was... whatever that can be described as. "The battle ended shortly after. The Serpent joined the fight, Lilith gave up and left, and her followers surrendered. After that, the Ringmaster started collecting the Mirror's shards while everyone else dealt with the wounded."

There's a pause, and then she takes the opportunity to ask, "What did you mean, a prophecy?"