sister is a fricken loser!!!

My sister is a fricken loser. She took a care aide course that ended in Dec only to not follow through with a job that landed in her lap and work at Walmart instead. If she wanted to work at Walmart for the rest of her life, why did she spend $9000 taking the course? I just don't get it. Also she has no ambition personally either: she moved back home with my mom (was supposed to be for only 3 mnths, going on 6 now) and keeps her room disgustingly filthy etc etc. I kinda want to cut her out of my life because she doesn't take anyones advice and snaps anytime anyone tries to help her/motivate her.