Hi, I'd like to help you with your question.
If your girlfriend used any type of hallucinogens during her years of drug use (either on purpose or by someone else giving them to her without her knowledge), then she most likely is suffering from drug induced psychosis. This is basically brain damage caused by the use of these drugs. The drugs affect an area of the brain called the temporal and frontal lobes. It affects a person's ability to reason and can cause all the symptoms you describe.
Your girlfriend's lack of insight is also another symptom. A person with a severe mental illness does not see they have anything wrong with them. They feel that what they believe is different and they are special. Or they just don't see that there is a difference at all.
Preoccupation with religions or religious beliefs is common with mental illness but harder to differentiate. Though it is ok to have faith (a person may believe that God loves them without ever seeing God, which is faith), but when the faith becomes a way to explain someone's different point of view or symptoms, then it becomes a tool rather than faith.
Many of the people suffering from psychosis or other severe mental illnesses become involved with cults so that may be why you are coming across this information as you try to research her symptoms.
If you can, try getting your girlfriend to a therapist for an evaluation. She may refuse because she does not believe she has any problems, but it is worth a try. She could also see her regular doctor (though they are not trained to diagnose mental illness they may know enough to help) and he/she may be able to help do a preliminary diagnosis. The doctor could also try to encourage her to seek help, maybe even referring her to someone in particular. The doctor could also order an MRI or other tests to see if he/she can determine if this is drug induced psychosis.
One of the best ways to help your girlfriend is to educate yourself and her family about having a family member with a mental illness. Here are some resources to help you:
When Someone You Love Has a Mental Illness by Rebecca Woolis
The Burden of Sympathy: How Families Cope With Mental Illness by XXXXX XXXXX Karp
Helping Someone with Mental Illness: A Compassionate Guide for Family, Friends, and Caregivers by Rosalynn Carter and Susan Golant M.A.
You can find these books on Amazon.com or your local library may have them for you.
Although you may not be able to force her into treatment, you can try to influence her to seek help and get answers. You can also support her and her family to help her live the best life she can.
I hope this has helped you,
I would need to evaluate her face to face to know for certain what is going on with her, just like a regular doctor would need to see you to diagnose. But if she does not have drug induced psychosis, then she could have either stressed induced Psychosis NOS (not otherwise specified) or late on set Schizophrenia. Women can get Schizophrenia throughout their lives up to age 60, although it is rare. Most cases of Schizophrenia are between the late teens to 20's. But it does happen. That is why she needs an evaluation by a therapist to tell for sure. It is highly unlikely that there are any other cause besides mental illness that could cause her symptoms.
Many intelligent people have a mental illness. It certainly does not reflect on her IQ that she may have an illness. I have heard a number of times in my experience about college students, including medical students, dropping out because of the onset of schizophrenia or other illnesses. Mental illness does not discriminate.
Yes, it will be hard if not impossible to convince her to see a therapist or doctor if she does not believe anything is wrong with her. It is a continual issue with people who suffer from schizophrenia, Bipolar disorder and other illnesses. They lack the insight to understand there is an problem and many of them, even if already diagnosed and on medication, will quit treatment because they feel nothing is wrong. And since your girlfriend is highly intelligent, then her ability to explain away her symptoms is going to be even more challenging and hard to refute. But I suggested trying just as a possibility. Sometimes you can convince someone with these types of symptoms to see someone. Even if you do it by going with them based on another issue, such as relationship issues. Not as trickery, but because their symptoms do cause problems in relationships or other areas of life. Most likely, you are not going to be able to get her to go. In that case, that is why I suggested you educate yourself and her family about mental illness and also get support through NAMI with support groups and contacts there. It will help you and her family cope.