She could be depressed, but sleeping late can also be (and often is) simply a habit established by those who have no structure (a job) in their lives. From the kindness if your heart, you are enabling this. Your marriage should come first and, you say, it is suffering (“at rock bottom”) as a direct consequence situation. If you insist she moves out, no doubt she will have a self-entitled tantrum (I have one of those daughter’s too), but she is used to physical comfort and being indulged. It’s a big, uncomfortable leap from that to homelessness. If you are serious, and stand your grown, preferably together with your husband. She will have no choice but to cooperate with moving into independent accommodation. The threat of homelessness is just manipulation. Given that she is used to having lots of time to herself due to you caring for your grandson, I doubt she will want to give that up. So I doubt that she will prevent you from spending time with him (another likely threat).
The next thread for friendship, advice and support if estrangement has affected your life
Not sure how to react anymore, am I in the wrong?