Sunset.
You have to decide on just one person, or just dump them all like what Squirrelflight did in the Warriors series.
Squirrelflight's father was Firestar.
Squirrelflight is Leafpool's sister!
Assuming that you are talking about Squirrelflight's big lie, Squirrelflight lied to protect Leafpool as well as Jayfeather, Lionblaze, and Hollyleaf from the truth.
Ashfur did not kill Squirrelflight in any book. He did attempt to harm her in "Sunset" (Warriors: The New Prophecy series) by attempting to push her off a cliff, but Squirrelflight survived. Ashfur's actions were driven by his jealousy and betrayal, but they did not lead to Squirrelflight's death.
Squirrelflight is not infertile. She and Bramblestar have kits together in the Warrior Cats series.
no squirrelflight WAS mates with Brambleclaw but not anymore,and ashfoot is a windclan she-cat
they didn't squirrelflight lied.
YES. in one of the books, Ashfur tries to kill the Three but Squirrelflight says that they aren't really her kits. Later, the Three unravel the web of mysteries and find out who their true parents are.
Firestar and Squirrelflight
Yes, Squirrelflight and Brambleclaw knew that Jayfeather was not their biological kit. Squirrelflight had taken Jaykit (Jayfeather) from Leafpool, her sister, to raise as their own after Leafpool was unable to care for him due to her role as a medicine cat. Brambleclaw was also aware of the situation and supported Squirrelflight in this decision.
Ashfur seems to have directed his hate to Squirrelflight. It can be assumed he believes that Squirrelflight, opting to choose Brambleclaw over Ashfur, was the one who was at fault. Maybe he thought Brambleclaw was an innocent bystander or something. If he did feel any hatred toward him, it's possible he simply chose to hate Squirrelflight instead, because he still loves her. Love hate situation.