I get the feeling that many "LOST" viewers had wanted Kate to be some ideal feminist character or near ideal character simply because she was the show's leading woman character.  Come to think of it, many had expected Jack Shephard to be some near ideal leading character, as well.  But here is the gist of the matter.  None of the characters were perfect.  In fact, they were very flawed and had fucked up lives.  These were the reasons Jacob had brought them to the island in the first place - so they could realize that living on the island (with one of them volunteering to become its protector) was a lot better for them than returning to civilization or continuing their off-island lives.

Neither Kate or Jack were ever meant to be ideal or near ideal characters.  Yes, Kate had her bad episodes.  But I can only think of a few of them that included (1.12) "Whatever the Case May Be" and (4.04) "Eggtown".  Most of her centric episodes were decent and perhaps a few were pretty good.  I can say the same about the Jack episodes . . . or episodes for other characters.

It took a recent re-watch of (2.09) "What Kate Did" for me to realize what laid behind a great deal of Kate's mistakes and crimes - namely her insecurity.  There was something she said to Jack in that episode that made me realize just how insecure she really was.  I also believe this strong, insecure streak within her led Kate to use other people either to bolster her own ego or give her some kind of emotional comfort.  

Kate had used a group of bank robbers to get at a toy plane that used to belong to her childhood love.  She had used the latter to get to her mother, Diane Jensen, inside a hospital.  Although Kate was in love with Jack, she did try to use him occasionally.  She used Sawyer to serve as some kind of substitute boyfriend/bed warmer whenever her relationship with Jack took a wrong turn.  She tried to pretend that she had murdered her father in order to protect her mother from further abuse.  But Diane Jensen knew the truth.  Hell, even her stepfather, Sam Austen, knew why she had really killed Wayne Jensen.  But the worst thing she had ever done (even worse than Wayne's murder) was to use Aaron, an innocent child, as a convenient emotional blanket following the Oceanic Six's traumatic departure from the island.