Are you a dead honest friend or do you lay low so you don’t potentially ruin the friendship?

Without getting into too much detail, a good friend of mine wronged an acquaintance of mine. (Acquaintance is out $450 directly because of my flaky, unreliable friend). I was stuck in the middle from beginning to end so it’s my business. My friend totally deserves to be called out on her shit but I also don’t want to hurt our friendship. Is it worth bringing it up?