Mmm, I don't know. You said you were once friendly with her, so you'd be in the best position to judge how she'd take that. It might just turn into the two of you trashing him--which he might deserve, but not sure how healthy it would be for the two of you.
If you think it might be something that would please her or comfort her, do, if not, or you're unsure, maybe you should let it be for now.