Guenever is sitting in her room doing some embroidery, and wishing Lancelot would return soon.
We learn that she has a bit more depth to her than Elaine does, because Guenever is a bit older and has more experience. She's "Jenny" to Lancelot, while Elaine isn't really an individual to him and he does not love her.
And just like she's summoned him, Lance shows up.
He figures that since that one thing he was so worried about was stolen from him, and that he's been unfaithful with Guenever in his heart, why not just go ahead and do it anyway?
And just like *that*, Guenever and Lancelot are together, just like Guenever has always known they would be.