A very awkward situation. If you let her violate the custody agreement, you win nothing. If you try to prosecute her, you also win nothing. Been there, done that. My ex violated the "within state" thing, too. My attorney cautioned me to avoid prosecution, but to try to get something in return. Maybe you could get an extra weekend, or maybe get her to agree to you taking your son somewhere for a special vacation.
I tell ya, divorce and custody do nothing to make people behave more reasonably. Everyone feels they got "screwed" somehow, so they're inclined to "get even" by doing something with the handiest football, the child. I think your ex is a lousy person. But don't sink to her level. Try talking to her, work something out between the two of you.
The only thing I can suggest is that you not identify the source of your information, especially if it's the child.
Technically, she *does* need the court's permission. In the real world, the court will hesitate to do anything punitive because that "offense" may not rise to the level of incarceration. I mention this because I'm not aware of any other punitive action that a court could take, if the court decided that this violation merited court punishment. But trying to punish her will bite you in the family court butt. Try working things out with her.
If she remains an unmovable witch, document what you can, then consult your attorney for possible action. You can always take your documented information to the court when you apply for a custody modification. No way to guess which way the court will decide. Courts tend to favor the mother a lot. Yeah, that's not fair, but it's a fact you gotta live with for another decade or so. Best of luck!!