Safety first?

Kristin • Mom of 3
Okay so I have a question. My friends Sister in law has a 6 month old baby. Forward facing since 4 months. Illegal and not safe, right? I informed the friend of this as she lives with them she blew it off because her mother is a "good driver". Now that may be the case but she might end up next to a bad driver or a new driver one day who makes the wrong mistake. How do I inform this woman without setting her off? She does does not particularly care for me. However I can't help but want to say something because it is her first baby and I don't want that baby to get hurt In case of an accident. Maybe she doesn't't know? :(. Help?!