The reason her TRV was refused was very likely not enough evidence that she will return. She will have to find some better ties to her homeland and emphasize that she wants to join her husband while he is in Canada and that they will both return when his visa expires.
The husband and wife (2 kids used to live legally(work) in the Middle East for many years before the husband transferred to Canada. Isn't this a clear evidence that the wife has no intention of illegally overstaying her visa?
Will a letter from the husband's company help in any way to assure CIC of their true intention of living together while the husband is on work permit?