How hard is it for my X Wife to get custudy of my daughter from me?

She will not receive custody, unless there are real problems with your daughter in your care.  However, since the court is in favor of parents being reunited with kids, if she takes the steps that a court may lay out for d. v. treatment, the court may start a reunification process that may result in a more standardized visitation schedule.      

If there has been no visitation for three years, there is no way that she will get custody right now.  It simply isn't going to happen, unless you are doing something monstrous to the child.

It's possible that she could get some visitation, to try and re-establish a relationship with your daughter.  It is a parent's right, ordinarily;  I suspect that CPS will have something to say about this, one way or the other, and that will probably carry a lot of weight with the court.  Courts don't like changing custody, because they understand that it's stressful for the child, even when it is actually necessary.