Help me out with a moral dilemma here. *all names have been changed to protect one guilty adult, one sad parent, and 2 innocent children.

There’s this woman that I know, Lisa, her and I used to be friends not too long ago. Our daughters are almost the same age. It was cute having them play and we would chit-chat. Her and I are extremely different in personalities, but we got along ok because our kids did. Plus, I’m the type of person that is amiable. I’ll shrug off a lot of things because I know how people are simply different.
Anyways.. Lisa used to take care of this baby named Emma. Emma was just a few months younger than her own daughter. Immediately, those of us who went to Lisa’s house for a playdate would notice that poor little Emma would stay in her carseat almost the entire day. If she wasn’t in the carseat she was in the crib “taking a nap”. The only time Emma would leave one of those two places is when one of us moms played with her because all of us got so sick of seeing this injustice.
Let me put it frankly, Lisa is a lazy bitch. She’s extremely obese and absolutely exhausted all the time to take care of 2 little ones. Renee (Emma’s mom) bought a double stroller for Lisa to use to take the 2 babies out on beautiful days… did Lisa ever go out? No. Those babies stayed inside all the time. When there was an opportunity to leave, Lisa would bitch and moan that it’s too hard with 2 babies.. although all of us would offer to help.
Some of us moms spoke on the side and said that at least Emma will be able to crawl soon and then walk so we won’t have to worry about the carseat thing anymore. True, but then we had to worry that she was in the crib half a day.
Lisa is entirely unfit to taking care of anyone’s children. She ignores them, spends most of her days on the sofa, plays on the computer a majority of the time, and is generally an unhappy person who would break out into “fits”.
So why didn’t I tell Renee all this? Because I couldn’t. Lisa and I had a huge falling out, and if I told Renee the truth would she have believed me? I found out recently that Renee was warned by Lisa that many women may contact her and say bad things about her taking care of Emma. All of us were seriously tempted to, but were worried we would be sued for slander.
Lisa is not taking care of Emma anymore, Renee has finally seen the light. One of my friends has spoken to Renee candidly and has told her everything she saw at those playdates. Needless to say Renee feels horrible. My heart goes out to her because if I ever found out someone had wronged my child…. I would feel unfit myself and guilty as hell. Then I could get pissed and plot to beat the shit out of her behind the Piggly Wiggly.
So.. my moral dilemma. Lisa is looking for a new charge to take care of. I think she’s unfit, possibly abusive, and shouldn’t even be taking care of her own kid much less someone else’s. She’s taken out ads on craigslist, and I just want to call her out on it and warn everyone. Can I get in trouble for that? Should I even do it? I just don’t want to see another baby harmed.