after bringing breezesong/star to fireclan, meet with her every night and talk to her. after 4-5 nights of meeting with her, she'll ask you to meet ryeheart and after that, you can now enter fireclan as you wish! ^^
after you kill firestar, she's in the warriors' den. you have to talk to her and say 'yes' when it asks if you want to meet up with her in secret.
