Someone else will have to help you there, unfortunately. I'm horrible with boundaries but lucky that for the most part I haven't needed many. She will spew at you and see you as the enemy but some boundaries in your case are needed and are more important for her respecting you. Respect in this case trumps the enemy view.

Only thing I can say is make sure you really have a well thought out plan with them before you do anything. Messing up certain ones can cause more issues than not doing it at all.

Accept what is, let go of what was, and have faith in what will be