Im crap at being comforting, but lets give it a go..
If you look at the statistics for covid in Canada (infections and deaths) there was an alarmingly high number of deaths compared to infections at first, but as testing has got better we are realising just how many people with mild symptoms went undiagnosed before, and more and better treatments have been perfected, so even though the confirmed infection rates are skyrocketing, the death rates after a covid diagnosis are LOWER than they were earlier in the year.
From the beginning in Canada nearly 270,000 people have recovered and only 11,000 have died, but we all missed a whole lot of the very mild cases in the beginning so the actual figures are probably a lot more favourable, your mother's chances of living arent all that bad so far, a good majority of cases end up being mild. As far as long term issues are concerned, I know someone who is suffering from this, it's given her heart issues, lung issues, kidney issues, its not great, but she is already back at work and being treated as an outpatient, though it is a royal pain in her arse, it isn't debilitating and she is recovering slowly.
You said the symptoms were still mild, so be cautious but dont panic yet.