Clean something!
I'm not talking about a basic dusting here—really clean the room you've chosen. Pick up and actually move things before you mop or wipe down. Windows have two sides to them--clean both!
Your best bet is to use cleaning products that your mom actually has (check under the sink). You don't want to introduce new industrial-strength sprays that might set off Mom's allergies.
When you're done with the deep cleaning, if you do decide to incorporate new scents, try something subtle, like a jar candle.
Courtesy of Yankee Candle
If your mom lives elsewhere, then try getting a gift certificate for a local cleaning service near her. Don't forget to check their reviews!