I am the one who looked after our mother throughout her illness. Should she give me a larger share than my siblings?

Your mother can honour your service with a gift while she is healthy, as long as the reason is clear and it does not wrong the other children. The Prophet ﷺ said: “Be conscious of Allah and act justly among your children” (Sahih al-Bukhari 2587). Some scholars understand this justice as equal shares, while others allow differences for reasonable causes such as service or need. So that it does not become a source of hostility, you could suggest that your mother discuss it openly with all her children. A gift made during a terminal illness is treated like a will, and is not valid for an heir without the other heirs' consent. There is also a gentler option: your siblings together pay you a caregiving allowance. See fairness in gifts.