Inspired by the Three B’s thread:
Which of the following do you think to be the best:
songwriter?
singer?
overall entertainer?
Carly Simon, Carole King and Joni Mitchell
Of those mentioned, I like Carole King.
With that being said, was Linda Ronstadt noted as a songwriter? Ann Wilson?
Joni Mitchell for all three. 
Laura Nyro.
Yes, Laura Nyro.
Knew you’d like that one.
Yeah, me too. But I’m not all that familiar with any of them; I’m not sure I could name more than one or two songs by Simon or Mitchell. My impression is that they’ve been out of the spotlight since their heyday in the Seventies.
Nope.
Of Heart? Yeah. But when I think “singer/sonwriter,” I think of a solo artist rather than a member of a band.
And yes, there are many other great female singer/songwriters, if we want this thread to go there.
How about Neko Case?
Or KT Tunstall?
You beat me by FIVE minutes.
(gets out New York Tendaberry to swoon over the cover photo for a while)
Songwriter - Cyndy Lauper
Singer - Judy Collins
Overall entertainer - Madonna (also best marketer)
Tanya Donelly
Tori Amos
PJ Harvey
M.I.A.
I would probably pick Kate Bush. Dolly Parton is more talented than she usually presents herself as.
TCMF-2L
Kate Bush, Indigo Girls, Melissa Etheridge, Cris Williamson, Tori Amos, KT Tunstall
Sara Bareilles
At first, wasn’t sure if you wanted us rate those three in particular, so what the hey I’ll go with Mitchell being the best songwriter, King the best singer, and all three have their own overall entertainment thing going.
songwriter - Chrissie Hynde, Suzanne Vega
singer - Debbie Harry
overall entertainer - Kate Bush
I’m going to throw in Karen Carpenter. It’s been many years, but I still get goosebumps when I hear her recordings. She really made me feel that she was sitting there singing to ME. Of course, she wasn’t noted as a songwriter, though she did contribute a bit here and there to her brother’s work.
Pretty sure the OP just wanted a ranking of sorts of the three women listed there, not “who’s the best of all time, here are my choices”, so it’s a tough call for me. I love Carly Simon, “You’re So Vain” is one of my favorites, so mysterious and somehow vengeful, like as if “You Oughta Know”'s anger had been channeled through a more mature and self-confident woman.
Joni mitchell is also phenomenal. Overall maybe the best songwriter.
Carole King might be best singer.
Since others seem to be doing it, I’ll post my own choices next…
I’m very familiar with all 3 from the OP.
Songwriter: Joni Mitchell
Singer: Carly Simon
Entertainer: Joni Mitchell
mmm
OK, deviating from the OP;
Best songwriter; ani difranco. Incredibly deep lyrics, very prolific artist. Voice works for her style of um, prog-folk-rock?
Best singer; maybe Floor Jansen of Nightwish.
Best overall performer; Anneke van Giersbergen. Excellent songwriting, proficient guitarist, and an enrapturing voice with excellent timbre.