The Muslim has to guard his tongue and avoid things that have been forbidden. Among these forbidden things which people take often lightly are gheebah (backbiting), buhtaan (slander) and nameemah (malicious gossip). Abu Huraira reported Allah's Messenger (may peace be upon him) as saying: Do you know what is backbiting? They (the Companions) said: Allah and His Messenger know best. Thereupon he (the Holy Prophet) said: Backbiting implies your talking about your brother in a manner which he does not like. It was said to him: What is your opinion about this that if I actually find (that failing) in my brother which I made a mention of? He said: If (that failing) is actually found (in him) what you assert, you in fact have backbitten him, and if that is not in him it is a slander. [Sahih Muslim Book 32, #6265]
You should become an example for other girls by avoiding all these things. It’s hard to give up backbiting for girls as they don’t consider it a sin but you can make them aware.