Wiz Khalifa's mom, Kate Wimbush-Polk, is suing Wiz's ex-wife Amber Rose for defamation.

According to the Washington County Observer-Reporter, Wiz's mom accused her former daughter in law of trying to ruin her reputation through a phone call.

In the suit, Wiz's mom said that Amber called her phone number, but a friend and employee named Danesa Lectic actually had the phone that day.  Lectic's 5-year-old niece answered the call, and Rose immediately started to bad mouth the rapper's mom to the little girl.

Eventually, Lectic got on the phone and told Rose who she was.  Amber kept on saying bad things about Wimbush-Polk, like she was responsible for Wiz's sister's death and unfit to take care of Sebastian, Rose's child with Wiz. Wiz's sister Dorien Thomaz passed away from lymphoma this past February.

[Related: Wiz Khalifa and Amber Rose are fighting about a bad threesome.]

It is believed that Rose made the nasty call because she thought Wiz's mom had called California child services on her, something Wimbush-Polk's lawyer denies his client did.

Wimbush-Polk's lawyer adds that his client is an upstanding citizen and mentors at-risk youth — which she has to get a background check for — so Amber's claims that she's unfit to watch Sebastian are off.

The suit further alleges that Rose damaged Wimbush-Polks's good standing in her community and now some people don't want to work with her anymore.

Wiz's mom is suing Rose for $50,000.

Do you think Wiz's mom will win the case? Furthermore, will Rose even care about being sued, since she's all in love with 21 Savage these days?