grown ass 14/15 year old

so me and my middle age step sister where talking about a conversation she had with our younger sister who is 14/15 saying she snuck an ordered a dildo off of shein a 17in one!! GIRL YOU ARE A CHILD!! should i tell my step mom or stay out of it. i’m 25 and my step sister that told me was 22. but the 14 year old is doing too much!