I did talk to a lawyer. We have equal rights to our S, so it is actually legal for her to take him across the state line. L also told me if I need helps from court, I better do it before her residency established. I will bring this up to her and see.... Hopefully she won't go postal on me....
I'm glad you saw a lawyer...it's always better to know where you stand.
Try not to worry about her reaction. The most important thing is to do what you think is right, not what will make her happy. If she is truly bipolar, no amount of evidence, reason, logic, etc. will change her mind. That is the pathology of bipolar disorder. Untreated mental illness can destroy the life of the victim and everyone around her/him.
Look out for yourself and your son. If you do those two things, the rest will fall into place.