Female rappers

Women are underrepresented in a lot of roles throughout the world. It is usually due to some combination of social norms, expected gender roles, lack of opportunities, and old fashioned sexism.
It's also possible you simply don't see many female rappers because it's not the music you seek out. There are lots of very talented women in the rap scene. Though they certainly do not get the attention they deserve (see the paragraph above).
Edit: to answer the second part of your question, I'll go old school and say Rebirth of Slick by Diggable Planets. Missy Elliott and Lauren Hill are top-shelf, too. Other people here have mentioned Doechii; she's a new star on the rise.
- I misread the title until I saw you said that "there are lots of very talented women in the [...] scene."
- Really you could put all of DPS and I'd count it. Ladybug is so cool, I love all her verses in any of their songs.

I really love Doechii, especially "Denial is a river". But her whole most recent mixtape is amazing. Also do checkout her Tiny Desk performance, she is the one to watch I think.
- +1 for Doechii! Her tiny desk concert is a great leaping off point for her work!
- Doechii is truly talented
- I was going to mention her Tiny Desk show. It's a banger!

Doechii didn't win that Grammy out of nowhere, her new album is really good. My kids love Roman Holiday by Nikki Minaj, I am less convinced but they do love it.

If you're looking for recommendations, everything by Missie Elliot is worth listening to.
She might be mainstream/well-known enough that it kindof "goes without saying", but just in case you're not familiar with her.

The majority of hip-hop I listen to is female. Tierra Whack (who imho is one of the world's all time greatest rapper), Latto, Glorilla, Megan Thee Stallion, Bea (despite the beef), Audrey Nuna, Young Miko, City Girls, Cardi B, Mariah the Scientist, Omeretta the Great, Doja, Ms. Nina, Renni Rucci, Lady Lashure, THOT Squad, Londynn B, LightSkinKeisha, REI AMI, Baby Tate, Tommy, Noname, Nitty Scott ... and so on
- I heard about half of your list. I'll check out the other half since I like the names I recognize.
- Thanks for this list. Doja is awesome.

Little Simz, Sampa the Great, and Snow Tha Product are some of my modern favorites

I'll echo what others have said and mention Rainforest by Noname (or any of her other music)

Gangsta Boo
La Chat
Zigg Zagg - Suicidal, The Argument pt 2
B for Better - What's the Point?
missink is doing some awesome battle raps on PenGame

Not sure but there's also not a lot female metal musicians, but I have a feeling that's changing more and more. Prolly just because rock n roll used to be a manly guy thing? I can imagine similar things used to be like that in hiphop?

Lady of Rage is one of my favorites.
Best known for "Afro Puffs", which I believe was on Dr Dre's debut album.
*edit: song title

Angel Haze. She hasn't released an album in a decade but she still comes out with singles every now and then. My favourite songs are "No Limits" and "Weight"
I also love Meg the Stallion's Tramazine album.
Notable mention: "4AM in Toronto" by Miloh Smith & Junia-T
Like a lot of male dominant professions, women often have a hard time gaining success in this industry. Whether that's because fewer female rappers exist or labels are just less willing to sign them, I don't know.