Morgan, as hard as it is, your friend has to take responsibility for herself.
Being a rescuer, especially financially will not help her, and it certainly will not help you.

I was in your situation once, and it got very messy and sent me over the edge, because my friend was also sick with drug addiction, possibly PTSD of some sort I still don't know as we are no longer friends because she didn't deal with her issues, and I didn't help by covering her where she should have done it herself. She lied to me, stole, use the money she had from welfare to take heroin and ice. Don't feed her issues -- she needs to deal with them herself.

She's a grown up. If my BB who has PTSD managed to get on in life with no family, or close friends then so can your friend. Rescuing adults never solves anything, she needs to take responsibility for herself. Don't feel guilty just because she is your friend.
Just tell her you can help her find a job/shelter and listen to her as a friend, but money, "no can't help you I got myself to look after."