Her verbrato has always been hard for me to replicate and even those that can don't have her distinct sound. Grace Slick also has hard to nail verbrato and pitch but it's within my range and many people range.
Stevie Nicks is the female Freddie Mercury to me. Neither artist makes my top 5 favorites but they are certainly unique.
Most Helpful Guy
Wow, you have some cool artistic interests and I like your taste in music. If I'm understanding you correctly, the epitome of vibrato is Janis Joplin I think.1