Sure, it'd be nice to know the person heard you. I mean, if she's watching TV or reading and you're talking to her, just eye contact would be enough to let you know she was listening.

I refer to Bruce's mom (we are not married) as Mom on cards and such. But I have never called her mom to her face. I could. But I just haven't.
She even refers to herself in cards and emails to me as Mom #2.