Sorry for your troubles - I've experienced cognitive impairment as a symptom of depression, and it is one of those things which have made everything else more difficult. It's a tough one, but I'll share a little of my experience and what has been useful for me. I can't say that it will be the same for you, but perhaps it could help provide a bit of direction. Note: though I've had a significant level of personal experience in a variety of treatments, I'm not a doctor or psychologist, and you should take my advice with that in mind.
- I've found that the best way to deal with the cognitive impairment I've experienced is to try to break things down into very discrete parts, once they're small and simple they're easier to manage.
-I've experienced transient hypomania from a couple of different treatments. That is out of nearly twenty medications I've trialed and a handful of non-pharmaceutical treatments. Antidepressants are not all the same, and an adverse reaction to one medication or class of medications does not rule out others.
-you have not said if your mother is a physician. If she is not, and even if she is, perhaps the problem is that she needs to get some information about how antidepressants are different? Feel free to show her this message.
-when it comes to medication, particularly when managing side effects and neurological symptoms, I strongly recommend getting a really good Psychiatrist and seeing them regularly. They will be able to build up the best understanding of you and how illness effects you, and will know best the treatments that can help. It isn't the easiest thing to find a good Psychiatrist who you fit with, I can give a few more pointers if you want.
-a good Psychiatrist will be able to understand, measure, and at least partially treat cognitive impairment.
-I find that sound can make my confusion worse, earplugs or headphones can help.
-short periods of work with regular breaks help me, if you look at 'pomodoro' time management I use a similar method.
-I use lists and careful planning to reduce my cognitive load. If you have a notebook it can help to offload stuff into it rather than try to hold things in your head.