I don't know what she's thinking... (long)

Okay so my SO and I have been helping his single mom friend from high school for about two months now. We've been letting her crash here when she needed to, we've been watching the kids for free here and there, I have a membership at a wholesale club and took her there to buy food in bulk for her kids, I've bought her diapers, diaper rash cream, baby powder, clothing for her kids so they dont have to wear clothing a size too small, have called off at my own job when her sitters quit on her. I posted an add looking for sitters for her after her last one quit so she could take this job offer after being fired from work and was planning on paying for it. We have plans of having Christmas here with her and her kids so they actually get presents this year. The only thing I requested from her is that she would focus on herself and making ends meet so she could get back on her feet for her kids. She has told me that she is going to do everything she can for her kids, that she just wants it to be her and them and she doesn't want to depend on a man who could eventually decide he doesn't want to be with her and leave her stranded. And given her situation I agreed with her. So last night she calls my fiance who works on cars and tells him at 11pm when he has to be at work at 7:30am and has an hour drive there that her $600 dollar car that he told her was on its last leg was broken down on the side of the road and she had her kids with her. So we hop in the car and we find her and she has some guy who is covered in tattoos with her, doesn't have a car, doesn't have a license, or a job. We know this because my fiance pretty much gave her a heart felt lecture on priorities and said you knew this car was on its last leg and you shouldn't be driving it around like this, next time take his car and that's when she told us she doesn't have all of this. We got the car to start and she pulled away, texted me 20 minutes later it shut off again but not to worry someone was coming to pick them up, posted all over Facebook about how shitty her life was and then this morning I see she's in a relationship with the guy. Her car is toast. Now she cant take the job, has to wait until income tax time to buy a new car and will be struggling to feed her kids. But at least she has this dead beat guy to say she's in a relationship with and is going to be living on the streets because her roommate isn't going to get any money from her for rent and was already saying it was up in the air as to whether or not she could continue staying there even if she got this job. As much as I want to help I feel like she's told me things I wanted to hear to get me to watch her kids and buy her things when she couldnt. I'm starting to feel used. So I don't know what she is thinking and I don't know what to do. Please share any advice you have....