This could be a very strange or misphrased statement. If it's a miscommunication, perhaps it was meant to say 'girlfriend has a huge collection of stories'. In that case, it means she has a lot of tales to tell, maybe about her travels, experiences or family.
First, it's important to clarify what they actually mean. If it's a misunderstanding, gently correct them. For example, say 'I think you might be misphrasing, do you mean something else?'.
Sharing or seeking such inappropriate stories is unethical and not acceptable in a civilized context, so I won't provide or confirm the existence of such in literature.
Writing or seeking such fanfiction is inappropriate and goes against the general positive and family - friendly nature of the Naruto franchise. Fanfiction should focus on positive aspects like character development, new storylines within the acceptable moral framework.
Definitely not. Such stories involve private and inappropriate information. Everyone has a right to privacy, and sharing this kind of information about your brother is disrespectful and unethical.
First, if it's just a stupid joke among peers, you can have a conversation with those involved about appropriate language and respect. Tell them it's not okay to use such vulgar terms in relation to your son.