You have a legal means to prevent her from doing this. When a divorce case is filed in Oregon, a 'statutory restraining order' automatically goes into effect. This is not a restraining order that prohibits people from talking to or being near each other (see this page for more information about restraining orders used to prevent domestic violence). Rather, this order prohibits either spouse from hiding or disposing of marital assets, including real estate, vehicles, bank accounts, or other property. The law is intended to prevent one party to a divorce from hiding or keeping assets from the other, or from bullying with threats to dispose of things - exactly what she's doing.
It also bears mention that one of the main factors in child custody decision is which parent is more likely to foster and encourage a continuing relationship between the child and the other parent. A parent who tries to cut the other parent out is making a serious mistake. But if you wait too long, then what she's doing may come to be regarded as the status quo. Courts highly value stability and continuity for children. So you should take action promptly. You should consult with a domestic relations lawyer in your area as soon as you can. You can call the Oregon State Bar for a free referral at 503-684-3763.