How to deal with my brother's girlfriend?

Ok my brother and his girlfriend have been going out nearly 4 years . I like the girl, she is fine . But since summer started i'v noticed she has been here EVERY day. The two of them do nothing. The just seem to watch telly all day and eat all our food. they seem to have no appreciation for money. Money is tight enough as it is and my parents getting food for 5 children living at home is hard enough without feeding another person .They dont even try to get jobs . And I thought when they went back to college she would be here alot less but the two of them are living at home except she is pratically living at our house now . I feel i have no comfort in my own home with her there all the time . For example yesterday i came home from school early because i felt terrible and there she was i felt i couldnt relax. They do not clean up after themselves leaving the place a mess and do not give anyone any space. My two sisters and other brother feels the same . And my parents notice the extra money being spent on food . what should i do?