As someone who wears both hats—that of former drinker, and that of family related to drinkers (mother and spouse), here is my take on it. I think your earlier talk shook up her status quo, and she went on best behavior to try and get you off her back about the drinking so she could get back to it, and then when her brief sobriety did not take your attention away from imminent separation should she continue to drink, she drank anyway.
None of that is your fault in any form—you just told her what you needed, and she was unable to manipulate you as she had in the past by a little good behavior, and because she is addicted she drank. What she did was exactly what I have done, and had done to me, many times. People have patterns of behavior, and we enact them to get what we want.
Your saying you are no longer going to continue enabling her drinking by continuing to live with her and do all household chores, financial support, etc. broke the expected pattern, and I think that’s a good thing. Now you have to mean what you said and stick to it, or it shows her that your boundaries are meaningless and she can keep drinking no matter what you say or do. That’s the hard part because you love her.
I’m sorry that she didn’t stick to sobriety and I know it must be especially hard for her given her additional mental health and employment issues, but you have to take care of you and in one sense you are helping her by not letting her easily continue the self-destructive behavior by keeping the status quo. She is an adult, and has the right to make choices—but so do you and please don’t forget that. Moving out on May 1 may be the very best thing that could happen in this situation, because you will get some space and she may choose to get serious and get some help with her problem.