What should I do about my mooching friend?

You sound like a really nice person and honestly I realize shes had a hard life but she needs to take responsibly. She needs to grow up and get a job. I know your trying to help her but your not always gonna be here for her so talk to her about this and ask her to find a job and give you some space and buy her own things. Ask your parents to not let her come into your house so that you can focus on you. You can't spend your days worrying about her. your only 18 so your have to worry about you. I really think you should dump your friend, gently.