There's No Female Version of "Manchild"...

[Oopity]

...because deep down society knows its redundant to add the suffix "child" for women

 

[Tesarossa]

childish bitch

 

[horseman.]

Good theory bro

 

[samo.]

woman child

 

[Oopity]

childish bitch

Its the default assumption

woman child

This isn't the same one word expression though, way less common and more forced

Good theory bro

Danke