How to solve my mom's death - HELP!!

My mom mysteriously died 6 years ago. Now that I'm financially stable, I can try to go and figure out what happened.

There was a massive cover up in my family and I don't even know how she died. I wouldn't let them pay me to be quiet

I've tried contacting her boyfriend at the time if her death but I've gotten no reply. I have no idea how to even START looking for answers. She lived in a different state from me!