Should I tell my friends mom that she is trying to get pregnant? Advice needed

My friend and I are 15 and we’ve been good friends since preschool aged. Our moms are friends and that’s how we met. I spend a lot of time at their house and I am pretty close to her mother. My mom doesn’t live in this area anymore. I live with my dad and stepmom and don’t see my mom often and I don’t like talking to her much so I don’t really. But I still go to my friends house a lot. My friend and I both have boyfriends and have both had sex but my boyfriend and I use condoms. They don’t use condoms and she wants her boyfriend to cum in her. She told me she wants to get pregnant and made me swear to not tell her mom. But I obviously don’t think it’s a good idea for her to get pregnant. I’m afraid if I tell her, she will lie about me and that her mom will tell my parents the lies, causing my parents to force me to live with my mom and abusive step dad.