Sis, do you truly believe that mental "illness" is a physiological problem - as in, a brain chemistry or other physical type of disorder?
I've posted antipsychiatry.org elsewhere, with their many links at the bottom of their page. It's a secular site but that's what we need to disprove the secular theory of what causes one to behave abnormally/irrationally.
I believe the help for her - if she's truly a Christian - is no different than what you and your husband are already quite acquainted with.
You'll recognize these links and I felt to post them before the entourage of replies come and opens that door again.
Once that topic is re-opened - there are few that care to involve themselves to untangle the web that can cause the young or vulnerable in Christ to get tangled up in - ie. 'deceived and debilitated by'.
The second link is from a link off of the first link -
http://inerrantword.wordpress.com/2010/10/26/contending-with-the-devil-jude-9/#more-164
http://www.spiritualwarfaredeliverance.com/html/christian-demon-possessed-no.html
I understand that you believe in pre-trib, but nonetheless - we're living in very dangerous times that will only get worse spiritually and we surely don't need to feed the vulnerable any more of the nonsense that we've seen within this year here.
As things get worse in the world and lies are perpetuated as fast as technology can move - Unless a person is solidly grounded in The Word and where they stand in Christ - the future will be very dismal for them. Deceptions could over-take, victories lost through fears and lies being fed into their minds by the enemy of their souls, etc.
As long as one believes either lie - 1- that Christians can be demon indwelt and 2- the myth of mental "illness", the future indeed will not find them in a victorious state because both beliefs are from the father-of-lies to begin with. To believe a lie is to sink - as you well know.
To believe a lie is to be accountable before GOD for lessening the work that Christ did upon the cross. Once a person has lessened His Word on our behalf, they are wide open to attacks of lies from the enemy or the secularists of this world. Fear sets in and they have problems being delivered after a while. The whole of our warfare is not believing any lies against His Word. The "imagination" itself is a mighty powerful force, once a person believes any of these lies.
"Behavioral" problems are no different than what people go through in these false revivals. The way to deliverance from these behavioral problems is no different than what you are familiar with, as far as how to be set free from that deception.
If the person who has behavioral problems is told that it is because there is something physically wrong with their mind and they need meds to stop their irrational behavior - they'll 'buy that lie' rather than get GODLY counsel, as those who have come out of the false-revival movement have received.
Once a person buys the mental-illness lie that was cooked up by secularists and worse - they have 'believed a lie' and are now subject to not having to truly deal with their behavior and the lies that they are now increasingly buying on a daily basis with this 'label'/diagnosis is setting them up for the ultimate fall eventually or soon enough.
Error breeds more error, and you know the rest.
Unless the person has been exposed to some bacterial, viral or fungal infection of the brain that causes a form of encephalopathy or a brain injury, the causes are not physical. The line between sanity and insanity is in how a person 'chooses' to "cope" with what life throws at us.
If the person is a Christian, they need counseling to un-believe the lie of mental "illness" first. If it's a case of PTSD, the healing comes about the same way, by renewing the mind by The Word, prayer and working through faith, with obedience. The rest is dealing directly with the irrational, un-Biblically based thoughts that precede the unscriptural behavior or 'acting out'.
The thoughts need to be renewed by The Word of GOD and prayer and a desire toward 'willing to do the will of the Father' -- so free-will is the issue in this, very much so. Many times we find that the root of such problems is unforgiveness, self-pity, the desire for attention, or hatred or resentment toward someone in their lives.
Rebellion is as the sin of witchcraft and that word in the Greek that's translated as witchcraft is "pharmakeia" - where we get our word "pharmaceuticals and pharmacy" from.
There is no condemnation for those who have believed a lie and forgiveness is full and free to those who have given into to unscriptural behavior, of course. They need to begin to un-believe the lie and take responsibility for all of their actions and will to do the will of GOD - being transformed by the renewing of their minds by The Word, prayer and obedience. Taking every thought captive to the obedience of Christ. The same process that those who believe any lie would have to go through, except for the fact that their body now needs to be weaned from the pharmakeia. All of this can be called a process of 'healing', as a person sets their face as a flint toward Him - He is faithful to move on their behalf, once the lie is renounced and responsibility for ones behavior is received back by the person.
Loving the them, fasting and praying for them and taking them down the road of responsibility for their own actions, according to His Word and by the Word, is the path to freedom. Irrational or sinful behavior will always be something that we are and will be accountable for, before GOD. Even the unsaved. I know that sounds 'hard', but I see nothing less than that in The Word. Only those who teach that we have no free will would say otherwise.
Even those who were abused as infants can be healed by the same means - as unbelievable as that might sound. Our GOD is a mighty powerful Creator and knows exactly how to heal those that He's known from before the foundation of the world. There are many potential super Saints / Overcomers out there, just needing to un-believe a lie or two.
I understand that what I've written goes against the tide of what we've heard since Freud, etc - but being sola-scriptura will always be against the tide.
His Love & Grace to you & yours.