It might be nice to add default messages that can auto-populate the date so she won't notice if network goes down for awhile or someone forgets to post a message.
This assumes the mother can form the new memory required to remember to call in that situation, which she by definition of the disease can't.
It (hopefully, theoretically) shouldn't make that assumption. It only relies on her apparent natural tendency to call her kids when/as she believes she hasn't heard from them in some time.