I dont think this is denial - it is shock, grief, sadness that you are trying to hold in but keeps leaking out despite your best efforts.

Your grief for your mom shows just what an amazing person she must be and the love you have for her.  You are grieving for everything that may come and everything you may miss. 

I would say this is normal and part of the grieving process.  You dont know when your mums time will come but just that it will be sooner than you or she would like so the grief starts with that knowledge. 

There is lots of support on forums such as this as well as through other channels to help you make sense of what is going on, how you are feeling and what to do next.

My contribution would be:  do what works for you.  I do believe that it is ok to say how unfair this feels (and is).  Yes, we all are brave and strong and positive but sometimes it is ok to say how not ok it is, how not strong you feel or unbrave. 

thank you