There are quite a few personnels who speak English in the airport. If you still can not find a one to accompany your mom, write her some notes such as " Can you find me a Chinese-speaking personnel to hel me" bla bla.
For the Ottawa airport, you may ask to go into the terminal with your mom due to her language barrier.
Or you can wait outside, they will ask you to come in when they find that there is a need to communicate with your mom. This is how my mom went back to China by her own.
Don't worry, but be sure to teach her how to read the bulletin board for gate change.
Good luck.