Talk:A is for Answers/@comment-166.137.89.170-20140606174716/@comment-46.24.224.251-20141018125107

In that clip: Mona says that she finds Alison as VD and she is spying on someone (she says that at the Mask....-ball in 2x25). Later, when Spencer know that Mona is A, Spencer says "You didn't see Ali in Brookhaven, she saw you"

Which comes to my conclusion: Alison could still have been spying on A, but not knowing it was Mona.