Written Defamation

Hello I have a friend who needs an advice regarding social media written defamation. The scenario is this: She joined a networking company and invested money on it and there was a glitch happened so they refunded my friend's money. Now, even if they called it quits, they kept on informing their members that my friend who already got her money was able to get the payments of her recruits which is not true. The founder was the one who said that to her subordinates. Question is can my friend file a legal case maybe written defamation and cyberbullying to that founder? If yes can she use the screenshots from her friend's conversation to that person? How strong will be the case for her? We need answers asap, we hope that anyone here could reply and give a good answer this is quite serious. Thank you