"Ladd" is a slang term for a young man, often implying a somewhat immature or irresponsible one. It's not a word with a traditional gendered counterpart.
If you're looking for a word to describe a young woman with similar connotations, you might use terms like:
* Lass: This is a traditional term for a young woman, often used in Scotland and northern England.
* Girl: A general term for a young woman.
* Chick: A slang term for a young woman, sometimes with a slightly negative connotation.
* Broad: A slang term for a woman, often considered to be outdated and offensive.
It's important to be mindful of the connotations and potential offensiveness of the words you use.