Should I tell my friend what her sister in law has been up to?

My friend is a hoe. And it sucks but it's true 
  I mean she's fun being around and is a good person (not including that she is cheating on her husband ) everyone knows she's sleeps around and a lot of the guys she's been with have no shame admitting it and talk so much shit about her . Very embarrassing things  like she smells bad and that she has a bush(that's her preference she doesn't have to shave if she doesn't want to) and more things 
thing is she's married her husband is gone for work everyone knows she's married but he's gone as of now. I met her husband first only because he's friends with my cousin and he came up to graduation party . So I met him and several years have past and he got married to her. I'm good friends with his sister and she always tries to get info out of me about his sister in law since she's heard some things about her and never liked her. Should I tell her about a lot of guys she's been with saying she gave them an std? Only for her brothers safety when he comes back. I know this will end my friends ship with her but she's not right for doing that. 

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