You can sue a ham sandwich. So, yes. You can file a lawsuit.
But you won't win. Name calling is not illegal. Name calling is not a basis for a lawsuit.
She can call your daughter a slut. She can call you a psycho. She is allowed to have her opinion.
And she's allowed to express her opinion. And if you filed a lawsuit complaining that your husband's ex called your daughter a slut, the judge would dismiss your lawsuit for lack of damages and would probably enter a finding that this was a frivolous lawsuit and order you to pay damages to the ex.
Frivolous lawsuits like that are why our court system is overloaded and broken. Just accept that she is a stone cold b*tch and a despicable human being for saying that about a child. She didn't do anything against the law, but if you can prove she acts like that toward your daughter repeatedly you may be able to have something done.
Unless the kid is directly in harms way, let it go.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.