To address the statement that is bold I did manage to unearth a single news report that had Molly Dilts and Barbara Breidor working together on Pacific Ave. So it would appear that, yes, the first two were acquainted.
After reading numerous reports on this case I did get the impression that Ms. Dilts would latch on to someone and not let go. Kinda like the lonely puppy that you can't quite shoo away. One report had Papa Joe kicking her out of his boarding house for sleeping in the hallways. Even the crack heads wouldn't give her a place to crash for the night. So, yes, she was vulnerable.
On the surface Ms. Breidor would appear to have a bit more street savvy than the others having lived and worked in the area for 20 years. She was the closest to being a local of the four. No reports of her eating at Papa Joe's and it's really not clear what part of Pacific Ave. she worked.