I think the issue about posting them public on the callboard is anyone can see them; not just other actors, but crew, the public, the cleaning staff, reporters, anyone who makes it backstage.
Notes given via e-mail are private - it's really no different then actors gathering in the house and the director giving out the notes verbally, right?
If the actress had an issue; I would talk to to the director directly, and see if they can e-mail me the notes, and I could take the time and divide them by the actors.
The rule in the LORT Book is:
(4) Individual Actor notes may not be posted on the call-board, except in a sealed
envelope.
This does not say that all actor notes can not be distributed to all other actors, although we as stage managers understand that usually you want to give individual notes to individual actors. Reading this rule, it doesn't seem like it would be against the rules to print out notes for everyone and put in individual envelopes.
Again, I think this is one of the rules that many people assume means one thing, but the letter of the law seems to be less restrictive. I think we all tend to think the call board for in-house communication only, but you would be surprised who stops by and reads the callboard during the day.