Yes, some people are like that. One may be the "leader" in abusing and the other "follower"

Your friend is being emotionally abused and that's the reason for her depression. The longer she stays in that household, the tougher she'd find it to move on and live a satisfying life.

There are 2 good news here - 1. Your friend is 18 and can legally move out. and 2. She has a concerned friend like you.

In an experiment done eons ago when animal rights activists were mulling over their existence, a group of psychologists, locked a dog in a cage and administered electric shock to cage for a few seconds. The dog used to yelp out of pain.

In the second stage of experiment, they had 2 set of dogs - those dogs that suffered electric shock previously and new set of dogs who were never shocked. They put the dogs inside the cage....but kept the door open. The dogs were free to get out.

The psychologists again administered electric shock to the cage....the news dogs ran out to escape the shock n pain...but the old dogs continued to remain inside the cage and suffer from the electric shock, even if they were free the jump out.

No one can 100% explain why those dogs continued to remain in cage and suffer....but it does explain the situation your friend is in. She'd continue to suffer with her parents and slip downward, feeling more helpless and trapped with every passing day.

The psychologists also experimented on what could make the old dogs escape the cage and they noted that they had to physically take the dogs out for the dogs to make that connection that they can escape....even if the dogs knew how to get out.

Your friend will not try to get out unless pushed, prodded and forced to get out. You can really play that role. Encourage her to get a job...maybe you both can move in together in a rented house? Constantly keep showing her apartments she could move to and jobs she can do to get out of that house.

You both can exercise together....the reason is exercise releases endorphins that would make her feel good. Exercise also makes a person feel more in control (thus enabling them to take action). The only side effect of exercising together is that you'll get healthier.

Also, encourage her to enter this Psychcentral forum. Sometimes, people who know and understand your suffering can help more than friend. So here, she can open up more.

Once she makes enough money, she should try enter therapy as soon as possible.

Good luck! I hope it works out for your friend!