Sorry about your grandma Great you've found support IRL.
No, I didn't. 3 of my grandparents died while I've been with this T and I never felt the need to inform him about it. Though I never feel the need to discuss with him anything via mail. If stg is urgent, I'll ask for additional session and if not possible I'll wait for my time.

However, I'd say go with your guts. Do YOU want her to know? Then mail her. If you truly "just" want to inform her Id say wait for the break to be over and tell her then.