While I think in general that drug dealing is, to put it lightly, not an ideal occupation for a parent, for a lot of people your kids are still your kids, and she could've been a great mom in spite of anything else.
Not saying I won't feel very angry if it turns out she's in some way related to this happening to this poor girl, but I can imagine her being destroyed by it, the same way anyone would if something happened to their child - and even more so if they were at fault in some way.
Also, while there are pointers to the contrary, the charges against her were dropped, and it's possible that she was just in the wrong place at the wrong time. Maybe this is more about people making sure someone who knows something doesn't tell anyone about it. Not saying it is, just that it could be.