Would a written letter or email about no contact be good? It's something tangible that she can read over and over again. Or would that come off as spineless and weak? Idk, have a lot of studying to do!
E-mails are weak.
Best to say in-person, and then FOLLOW UP with an e-mail, confirming what was said.
"What is best for my kids is best for me" Link to quotes: https://www.divorcebusting.com/forums/ubbthreads.php?ubb=showflat&Number=2879712