Instructions
Ignore Lady Grey after you have married her. If you continue to avoid interaction with her, the game will warn you when your marriage is in danger. You will be prompted when Lady Grey has chosen to dissolve your marriage.
Attack Lady Grey repeatedly. Unlike other possible spouses in Fable II, Lady Grey cannot be killed. However, repeated attacks will damage your relationship with her and culminate in divorce.
Flirt and make romantic overtures toward other characters when you are in Lady Grey's presence to damage your relationship with her. Drinking often can also raise the possibility of divorce.
Invite Lady Grey to accompany you while you partake in "evil" acts, such as killing good non-player characters. This behavior will eventually damage your relationship to the point of divorce.