You were right. EA started a long time ago. PA happened over Christmas, after she dropped the bomb. Confirmed with W and a mutual friend.
I confronted her. She tried to deny it at first, but then admitted. Told me she's had feelings for him since she was 17, and she was burying them because she wanted our marriage to work. Until about August.
M:31 WAW:25 T: 5 years M: 6/25/10 Bomb: 12/17/10 Discovered PA 1/2, Discovered EA, 1/17 Served D: 1/27