12 year old niece says she’s bisexual

Hi Nicholeen I have a friend who is wondering if she should tell her sister-in-law that her niece says she's bisexual? My friend's husband has three sisters and about a month ago my friend and two of her sister-in-laws were talking and my friend was told that their niece told them that she was bi. Their niece told the 2 aunts last year. Their niece is 12 years old. Since my friend now knows this info she is debating if she should tell the mother of the 12 year old who is one of her husband's sisters. She doesn't know if the mother should know or if she should stay out of it ? The mother and 12 year old don't have a good relationship and things aren't well in the home and she will probably yell at her daughter and be angry that the sisters knew so long and didnt tell her. Thank you!