In preparartion to ask her to move out, i wonder if i should communicate this over e-mail?

I'm trying to find a way that expresses and recognises that being under the same roof is making things tense and stressful. That for our own mental health we change the status quo. I think the new year would be the best time, so the children don't associate this time of year with upheaval/upset etc. I want to word it so that it is clear to her that she should move out as she has brought about this sitch, but be mindful of being respectful to her role as a Mother. She is a great Mum, and i don't want to deepen any resentment towards me!

How have others living under the same roof approached this?