My condolences on your loss Liam.
Unfortunately your questions about her mortgage aren't easily answered as each case depends on a number of factors. Did you co-sign the mortgage? Was it a joint mortgage? Did she have life insurance on the mortgage? Did she have a will and if so are you the executor of her estate and were her "assests" left to you upon her death? Each case is different and there are so many variables involved.
Even though the mortgage company has been informed of her passing and they haven't made any communications to you specifically that does not neccessarily mean that you are not responsible for the repayment of it. Just like with Revenue Canada the excuse of "I didn't know" does not apply. It's up to the individual to make sure they have the information and knowledge they need. I'm going to agree with Colleen here and suggest that you get legal advice. You're going to need a lawyer to "probate" her will and a mortgage is usually part of the "debts" that the pay out of the estate covers.
Don't panic just yet but do make the needed inquiries. In the long run it will save you a lot of grief. I know that you don't want to "stir things up" with the mortgage company but the sooner you find out from them what is happening with it the better. It may not be as bad as you fear but you're going to need to contact them one way or the other to find out the status of the mortgage.
I'm sorry that you have to deal with such worrisome things at this time and do hope that things work out in your favor.
Razz