i have a slacker coworker that drives me crazy he gets to work late everyday and does the minimum to get by
Is the boss aware or does he seem to skate by unnoticed? 
she is aware but doesn't feel the need to do anything about it. that's what makes it worse
Is there an HR department you can take it to?
not directly inhouse
Sounds like it might be time to sit down with the boss and discuss your thoughts and feelings. If moral gets too low it's not good for anybody.
i've tried. she says she will talk to him but nothing changes.