What is Proctor's response when Abigail speaks of her love for him?
I assume that you are talking about the part in Act I, Scene 2 where Abigail tries to talk to John Proctor about the affair that they had together.
The only time that she actually uses the word "love" is at the end of this part of the scene. She says that he loved her and still does love her. At that point, the stage directions say that he turns to go, but he stops because Betty starts making noises.
In general, though, Abigail is talking about what she and Proctor had together throughout the scene. During the whole conversation, Proctor consistently tells her that what they had is over. So I would say that his response to Abigails talk of love is to tell Abigail that he does not love her -- that their affair is over and he loves his wife.