She couldn't not be a Slayer when she saw how it was impacting her life. She saw that demons were real and they were killing people she cared about. She did what she had to. She died.

She knew that demons were real all along. She didn't like Jay letting Sebastian drink his blood, but she didn't do anything about it. She didn't try to kill Sebastian. She didn't try to kill any of the vampires, except for the one who stole her boyfriend.

She attacked May in a fit of jealous rage - no noble motives to defend humanity here - then basically gave up and let Alex kill her.

I don't see how any of that shows "being a Slayer" impacted her life in any way until the very end.