Its hard to know for sure that this question is sincere with out being involved personally with the circumstance. And it could be possible is that the daughter is either going through a mental or spiritual problem. If you trust your daughter and step children then its likely a spiritual attack.
I’m not saying its easy to figure out since you probably never faced this before and it is a family memebers whom you love, but its possible to find out what the problem is.
If you have good health insurance seeing a really good mental health doctor like a psychiatrist would be smart to have your daughter go to. Since you are there you’d be able to tell way better then other’s who aren’t going through it what is happening. If it is an emotional/mental problem get the best advice available. However, if its a spiritual problem I’ve had some experience with that, and the following information could really help.
On one hand if you as a father can tell that she is telling what she is really happening and you are convinced yourself it is the truth (being her father you should be able to tell by knowing her so long, and by her behavior) then it could be a spiritual problem. One way to tell if it is a spiritual problem is if your daughter, and even you have a terrible sense of gloom, darkness, and no hope when this stuff happens. If you and/or your daughter senses darkness it is likely to be a spiritual problem.
The bible says there are two major spiritual kingdoms in this world. One brings out the light through truth and love.
The other kingdom causes darkness through deception; fear and hate.
In my experience as a Christian if the ghost thing is for real then its likely a demonic presence trying to deceive, lie, and hurt your daughter.
The best way to handle it if it is really happening is to call upon the name of Jesus, repent of one’s sins, and let Jesus in your lives. Begin to read scripture, pray, and find out what the living God would have a person live like. A person needs to know Him to come against the dark forces who may be oppressing your daughter. It is a serious thing, but God’s kingdom is way stronger every time.
Then as a Christian pray with authority by the blood of Jesus that it must leave your home. In that prayer cast that darkness out, and have Jesus send it back to where it belongs; in hell.
A friend kept having his lights come on even after turning them off. It was a scary thing for him. But through
Taking authority in the name of Jesus, the son of God, that spirit or demon causing that had to leave the friend’s home. Although before it had gone on for awhile, and he didn’t know how to deal with it after the prayer it has never come back.
Satan has a real kingdom that causes these kind of things, however, Jesus said upon this rock I’ll build this church and the gates of hell will NOT prevail. It sure could be a similar thing.
May God help your daughter in either case.