My Long Distance Girlfriend Is Undergoing Oxycodone Withdrawal After Being

My long distance girlfriend is undergoing oxycodone withdrawal after being on the med for three plus years under a doctor's care. I now suspect she may be in a treatment facility as she's stopped communicating with me. Essentially, she's gone from being very communicative, loving, upbeat, and affectionate to someone who is very distant and apathetic about our relationship to the point that she either is not allowed to communicate (because she must be in some sort of treatment) or doesn't care to. What can I expect from her? Is this kind of behavior normal? How long do the psychological effects of oxycodone withdrawal last? I've had a difficult time getting a straight answer out of anyone in the health field on this.