Why can't a Muslima live on her own or with a female roommate? If she knows that it's best she does. I know in our country that Muslim females should always live with their parents, until they are married. But what if she doesn't not feel safe at home from her father or her brothers?

Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
If the woman does not feel secure among her father and brothers and if she fears for her honor, it becomes lawful for her to leave them and reside in another place provided that place is safe and secure. The person she lives with should be able to provide her with the security she needs. She might, for instance, live with a pious family making sure that she never stays alone with a non-Mahram man (marriageable man). She should have a separate room to sleep in or live with a group of females and this is more appropriate for her. She should stick to her religious obligations and rituals and avoid committing sins. If she finds a family where there are no young males that would be better for her. But she should not under any circumstances live with men, even if it is a group of pious and religious men. We ask Allah to protect this woman from all misfortunes.

Allah knows best.