From a survivor
I'm an emotional abuse survivor, so I'm glad to see this topic being brought up. All too often, emotional/mental/psychological abuse is seen as milder than physical or sexual abuse and something the victim should just "get over."
I agree with a lot of people here about The Devil because all abuse is cruel and I see that cruelty in The Devil. I also agree that the 8 of Swords shows the feeling of being trapped, which so many of us have.
I seem to remember reading somewhere that the King of Swords, reversed, can represent a control-freak (not necessarily a guy, of course). The person who mentioned The Empress as a smotherer (also not necessarily a woman) was right on--smothering is a very destructive form of emotional abuse (first-hand experience with that!). I also see the Queen of Cups, reversed, as a smotherer.
Strength, reversed, can express the helplessness of the abuse victim. The 3 of Swords can also express the sorrow and heartache and the 9 of Swords the despair.
I wouldn't be surprised if querents involved in emotionally abusive relationships who seek guidance from Tarot are mostly looking for validation. As caridwen pointed out, it's all about mind games, and often victims are given "logical" reasons why they're being treated badly. The "Am I crazy" syndrome is common with this type of abuse because there are no bruises or inappropriate sexual violations as "proof" that we're being hurt. Even just acknowledging that the cards show a hurtful situation that's disempowering the querent can empower some of them to seek help.