I need advice

So my best friend since 7th grade is now pregnant, I'm about to be a senior in high school, and she's asked me to be the godmother !! But my parents are really strict and wouldn't approve, so I do I tell my parents why I'm buying and making baby stuff. She's coming to my graduation and bringing the baby, so eventually they will find out. But how do I tell my parents she's bringing a baby with her??