I'm sorry to hear you and your family are going through this. I agree with her physicians that unfortunately it does sound as though your mother is approaching the end of her life and palliative/hospice type care is appropriate.Given your description, I suspect that her current condition is likely caused by hepatic encephalopathy, where toxins like ammonia build up in the body as they are unable to be processed by the failing liver. The treatment for this is usually medications that promote frequent bowel movements, like lactulose or other laxatives, as the bowel is the only other route by which these toxins can be removed.Hospice care should be focused on your mother's values and what's important to her. If you feel that it would be important to your mother to be more awake and with it during this time, it would be reasonable to ask her physicians whether medications to treat encephalopathy could be restarted. However, the counter argument is that by being more awake, your mother may also be less comfortable, the avoidance of which is another goal of end of life care. It could be that this is why her physicians have felt that holding these medications to promote her being less aware is best for her at this time. This is a conversation you should have with her palliative care doctors and together figure out what is the best way to care for her. Again, I'm very sorry and hope this helps.
You seem to have knowledge about how SSRIs work, wondering if you'd take a look at my post, possibly had SSRI-related damage happen to me. https://www.reddit.com/r/antidepressants/comments/raqwkk/my_life_has_been_upended_and_i_dont_know_what_to/