What is needed for an adult diagnosis?

Hello everyone.

Can anyone tell me what the diagnosis process involves for adults who want to find out if they're autistic?

I have a dear friend who strongly suspects that she is on the spectrum but is afraid to go forward with a diagnosis because she heard that the therapist(or whoever does these things) will want to talk to her parents or any family members that was around her when she was young.

She grew up in a mentally and verbally abusive home so the last thing she wants or needs is for her parents and siblings to know that she might possibly be autistic.

Thanks.

Edit: We're in Canada