I've been there, only fortunately my daughter was being responsible. However, when she got pregnant I told her and her boyfriend that they were now taking on adult responsibilities and needed their own place. Within a month they were in their own apartment. Fortunately they were both working.
Then, later after the baby was born, I was concerned about the baby's well being. Nothing to report to CPS but still not a good situation. I took care of the baby while my daughter worked and in this way was able to give my granddaughter what she wasn't getting from her mom. Her boyfriend left.
It's very difficult but tough love is a must. IF you don't set some boundaries now you will be living this frustrating life for years. Tell her that she must take care of herself. In order to live with you she must have a job and pay rent. Otherwise she's out and on her own. And then follow thru.
You can suggest that you'll take care of the baby until she gets on her feet. You can tell her you'll call CPS if things don't change. Use it as leverage.
As long as she's living with you, you're making up the difference in taking care of the baby and CPS won't get involved. You are providing what the baby needs. But you can insist that she move out and if she doesn't have a home and is not taking reasonably good care of the baby they will get involved.
Sounds like you need to have some definite rules for her to live by. As long as she's living in your home you can insist that she not have overnight guests. You can require rent, help with housekeeping, and a respectful attitude. If you want to not just push her out you can start with a conversation about responsibilities of adults in your house. Perhaps, tho it's unlikely after all these years of having no rules with consequences, that she'll straighten up. I would give her a deadline of say 1-2 months to meet these rules and tell her that she's out on her own if she doesn't comply.
Be calm and unemotional. Vent with someone else. Be firm and unwavering in make these requirements.
My daughter and I went for some counseling which helped us sort out our roles as mother and grandmother. As a mother it's really easy to want to take over when we see our grandchild being short changed. Reality is that the mother has all the power and for us to be involved we have to find a way to work with the mother.
You have the power in your home. You can make requirements for her to stay and you then have to follow thru with consequences. You have to let your daughter fail as a mother before you can take over.
My daughter woke up and became more responsible. She and I had a terrible time during her teens and young adult years but we worked thru our issues and are on good terms now. I give counseling credit for the greatest influence. Counseling helped me see that even tho or especially because I was concerned about my grandchild I had to back off and give my daughter a chance to be responsible.
Note: my daughter did allow me to take care of my granddaughter for 2-3 months while she did get on her feet. My way of talking with her was to avoid any accusations, to say to her that she had so much to do that I offered to help her by taking over the baby for awhile.
I'm sure she is eligible for state assistance including WIC. That would be a place to start. My daughter received financial assistance to by taking classes to make her employable.