Call her psychologist and explain what's going on from your end. He will have to get her permission to talk to you about her troubles. Talk to your step dad. There is really nothing more for you to do, it's up to her to deal with what demons that are causing her pain. Just tell her you love her and need her and she can call anytime she wants to.

What do you do when a family member is going crazy.
 

Sorry I meant no parfyness.

We're going through something very similar with a family member. It's tearing our family apart (not me and my wife), with the holidays approaching, it's always worse and something sets this family member off every year and the holidays end in tears and screaming, not at all pleasant. Best of luck to you and I hope you have a better way of dealing with it than we do....

Holidays are not pleasant when we're around either my sister or my mom so generally speaking - we aren't.

Last year it reached across the continent and brought me into it though...awesome...

Sorry to hear this Mike, it's a hard road. Dealing with this is a big part of my wife's profession. I know you may think she's too young but she most likely should see a gerontologist.

Depression is the number one cause of these kinds of issues. First she should be kept busy, social activities and physical activity. Funny as it may sound but something like square dancing is great as it mixes socialization, technical skill and exercise. Busy work keeps the mind off of what one thinks sucks in thier lives, whether it's real or imagined.

There are drugs, but forms of electroconvulsive therapy (ECT) have shown to greatly improve peoples lives when they have depression or dementia. If a doctor recommends ECT don't get freaked out, it's not like the old electroshock therapy horror stories of the past.
Electroconvulsive therapy - Wikipedia, the free encyclopedia

Hugh you're a good man for taking care of family, my 83 yr/old mum lives with us, so I know what it's like.

David see if a local hospice or retirement home does short term stays, sometimes just a temporary break and spending time with your spouse is all you need to keep your sanity.