Questions about insurance

The family life dynamic is difficult to explain but my mom is bed bound for a while and my stepdad has taken over everything concerning family matters.

I’m 20 years old, live in California, am under my parents health insurance. My mom and friends keep telling me that if I use the health insurance to get an abortion my stepdad won’t be able to find out since it’s protected health information but I guess if your parents want to find out then they can? I guess I’m just asking how is it that they find out specifically? Do they contact the policy holder or something? Like email, phone call, etc? Cause that would’ve been my mom but since my stepdad switched our insurance idk if that still applies. My friend said that even if they send a letter home it’d be addressed to me since I’m the patient. I just really don’t want to have to pay the 600 dollars when I know the health insurance would cover it. Thanks in advance.

At the end of the day my stepdad cannot find out about this “procedure” so if I use my health insurance how is he finding out about it?