GW, remember that a boundary is for you, not someone else. You have no way to enforce a boundary on her. If finding out about her contacting the OM hurts you, what can you do to minimize the pain on YOU? That's where your boundary should be.

Me-47,XW-43
S13,S16
M:18
BD:4-23-17
W filed:7-17-17
(5 months of in-house separation hell)
W moved out:1-6-18
D granted:2-15-18
Decree signed:3-29-18

Your future is out there. Go find it.