Perhaps practice varied, around the country. The expression 'hearing Mass' was never used where I lived. 
And the expression 'attending Mass' (which Jay used) wasn't used either; it suggests that the Mass is like a spectator event, which of course it isn't.
I see, from a  quick glance at the CCC (in its English translation), that the Church "requires the people to participate in the Eucharistic celebrations". Whether or not Holy Communion is received, one participates in the celebrations.
Your mother sounds like a good and faithful woman, may she rest in peace.