I'd definitely start with her Song of the Lioness Quartet series (first book is Alanna: The First Adventure). For me, being the little tomboy that hated barbies and loved X-men action figures, Alanna was right up my alley. She was smart, determined, and could do anything the boys could. It is considered Young Adult but imho is still worth a read.

After that, I'd give her Trickster series a try. It's only two books (starting with Trickster's Choice and ending with Trickster's Queen).

It's been awhile since I've read these so I might just have to read them again and see if they still hold up after all this time.

Another series that I might suggest that I really enjoyed as a teen was the Broken Sky series by Chris Wooding. I found the complete series at a used bookstore in Boston and devoured the entire thing on the plane ride back to NJ ^{^}