I know parenting can be frustrating. If W makes a pattern of this poor behavior, then you should be concerned. Personally I would just document things, and be extra observant. You can set some boundaries if she doesn't change her behavior.
This is the template: "When you leave our 2YO daughter unattended, I feel .... If you ....I will..."
Did you validate how W was feeling? That does not mean you condone the behavior, just that you understand how she was feeling.
"What is best for my kids is best for me" Amor Fati Link to quotes: https://www.divorcebusting.com/forums/ubbthreads.php?ubb=showflat&Number=2879712