"Slander" would imply that I had told a lie. I am not so sure that I did.

[She called him a foul mouth, nothing else!!! Nothing to be offended by here!!]

Unless you disagree with my verdict that most young ladies should not harbour any intentions towards your young master's heart- or other body parts- then I fail to see the problem. [Apparently it's either insults or encouraging Mabel to follow the bocchan route, no in between.]