I think this is an extreme of a complicated situation (made so by them,too).
All kind of human and artificial sciences should be considered equally as any other religious methods. The same must be done with psychology, psychiatry, and the other sciences or pseudo sciences (in case they help to achieve a good objective: to help human being or the person suffering from that illness or whatever they have).
Everybody has a past, a social hidden drama (a huge one in this case) and it does not mean they must have been 'possessed', if that exists. They 'think they are possessed' because that was they were told and taught.
Think about this: Do you think if they were not from Latin-Spanish originis, but from other Anglo-Saxon or let's say, Norwegian or completely atheist background, would they do exactly the same? I don't think so. Could have been her subconscious mind together with some drugs or punishment situations she din't liked very much? I just leave a logical idea for reasoning...
Madammes et Monsieurs! It's society! It's money and it is the Religion (or religions, in case we are dealing with any other destructive or ones)! Undoubtelly.
Remember Christ and good religions played with LOVE, FORGIVE, and even more things related with positive things we haven't reached, so don't believe anything you watch, see, live or whatsoever: Follow your heart and mind. Follow your natural Spirit and Pray in Liberty!
May God or the Universe, or even the positive force you believe in, helps you all your live!!
Netflix: The Devil Inside. (Insurge Filmes).