Ok yeah she did kill ashfur, but really, think about it, he was going to ruin her "family" and thunderclan. SO she killed him,Yes she did tell all the clans later on but thats because she couldnt live with the secret and maybe thought i couldnt stay a secret.
She tried to kill leafpool, but remember that she respected the warrior code and it was every thing to her. So when she found out that her mother, a med cat, had kits with a cat from another clan ( breaking the med code and warrio code) her was devastated. And on top of that, her mom gave her up.