Is there any chance you could talk to her about this rather than stopping living together right away? It sounds like there are advantages as well as disadvantages.
Could you sit her down, have a cup of tea and say:
"Mum, I am having a really hard time at the moment. As you yourself know, separating from your partner is never easy.
What I need is for you, as my mum, to be 100% behind me. I need to be able to recover from my relationship breaking up and learn how to be a parent on my own.
What you can do is be the most amazing supportive mum. You are already helping me with DS, which is wonderful, but I need him to respect how things are done my way. It's really important that at this time when our lives feel really out of control that I am taking a very strong parenting role for DS. Please will you support me?
I know you will as you're such a wonderful mum and gran. I know sometimes I will do things differently from you, but please help me out with this."
Or is that not the kind of thing you could do? I know my mum would love to feel she was being a support (she too is a hippie type) and would find it flattering being given a role helping me very explicitly.