Would you be angry in my situation?

No you are not silly! This happens all the time. It really pisses me off too!! Confront your sister and tell her to get it together... to stop being a lazy *** and start working more hours. I think you can report her to her social worker... and they'll start investigating her and why she doesn't or cant find a full time job. My "mother in law" had 12 kids!!! she doesn't work uses the lame excuse that she cant because there will be no one to take care of her kids. Her house is dirty looks like a dump. Roaches everywhere, she doesn't know how to clean or cook. She gets a EBT card which is reloaded every month with a little over 1200 a month... she gets the government to pay her rent.. and she never has money! shes a horrible mother.... a horrible woman... just a terrible person who tries to rip anyone off or borrow money from anyone. Its scandalous. THE BEST SOLUTION is STAY THE HELL away from people like this... SOON ENOUGH they will try to screw you over as well.....show ur parents that you are different and you an live on ur own and be responsible and independent. and tell them they shouldnt encourage her or smile upon her lazy ***....theyll get pissed but theyll be proud you are doing it on ur own and your sister will be nothing more than just jealous and bitter for her sorry *** life choices!!! HOPE THIS HELPED.