Looking for the title and author of the following short story:
The story goes as follows:
            A woman is visited by her adult children with bad news: the evening commuter train dad takes each day on his way home from work has crashed, there are no survivors.  The kids are concerned for mom, she is after all "elderly with a weak heart." Mom excuses herself from the communal living space to "lie down to rest."  As we follow mom into her bedroom we realize by her internal monologue just how freeing this is. Finally, after all these decades a chance for a life of her own.  There's a commotion in the living room, she comes out to find her husband is alive and well, he just got home.  He'd been running late and took a different train, he's fine.  Mom drops dead. Reader left to wonder: did she die from her weak heart and the roller coaster of stress, or because her husband is alive and she's not free?

I want to say it's from the late 40's - the late 50's?

I read it in school (college English 101?) in probably one of those Norton Anthologies.
Any idea greatly appreciated.
Thanks,
Jackie @ the Maine State Prison