True CW
Not bringing it up at all might come across as passive aggressive.
Also I have gotten some info she might not be feeling to well (from SIL and a mutual friend).
Don’t want to tip the scales in terms of anger/depression if you get my point.

Also I wouldn’t warn her, just let her know the envelope came and potentially ask if I I should open it for her.

Me: 34
Stbxw: 30
D:5 D:3
Mini bd: May/June 2019
Married: Aug 2019
BD: 6th Dec 2019
OM Confirmed: Feb 2020
March 2020: I filed for D
Waiting for D to be finalized and W to move out end of January 2021