I'm sorry to hear of your loss.

You can use TurboTax Online to prepare your mother's return. However, TurboTax Online doesn't have form T1255, which is needed if your mother owned a principal residence at the time of her death. You can download it from the CRA website, print it and mail it with the rest of her return. You can find form T1255 here: https://www.canada.ca/en/revenue-agency/services/forms-publications/forms/t1255.html