Why does she need to know that you're retaining an L? You can have an L who reviews and supports you through the mediation process but that doesn't necessarily mean you have to be in a "have your L talk to my L" situation.
You can't worry about how doing what is best for you and the kids affects her. She's given up that right.
Hugs! You got this.
Me (46) H (42) M:14 T:18, D9 & D11 4/19 - 12/19: series of escalating BDs 9/20 - present: R and piecing