There are a number of theories floating around on this.
1. She lost a baby/had a late miscarriage, husband blames her. Locked room is a nursery. (Initially proposed by
GGGRRRE I believe.)
2. Burke made some moves on her. Husband saw and left. She swore off men and their intentions as a result.
3. Husband went "breaking bad" (My own unlikely pet theory, a lot of things happened at the same time three years ago - and I don't believe in coincidences.) shattering her confidence in men and just hoping her husband would return to "the good" and to her.