A Plea for Prayers for My Beloved Mother

Salam alaikum dear brothers and sisters, I'm hurting deeply. My mother was a dedicated Muslim-she performed Hajj, never missed a prayer, and had khushu' in every sajdah. But three years ago, everything changed. My brother was diagnosed with bipolar disorder, and we found out he had been using drugs. My mother slowly fell apart. She started searching online, lost hope for his recovery, and began doubting Allah. Then she stopped praying, stopped making dhikr, and even developed resentment (when I asked why she wasn't praying, she'd say she couldn't; once she admitted she kept questioning why her child got sick while others' children are fine). Eventually, my brother got better-the medication worked and he's living normally now-but my mother only grew worse. She still doesn't pray and can't escape her depression. I feel guilty because I live abroad, while she's with my father and brother. She barely leaves her bed; they have to force her to walk and eat. She says strange things, like she'll die because of a dream, and she's terrified of death. My father and brother are gentle with her, so they let her stay in that state when they get tired. But when I visit, I take a firm approach. I don't accept "no"-I raise my voice to get her to eat, go out, and pray, even when she curses me. And I see improvement: after a week, she starts moving on her own. But once I leave, she declines again. I hate that I have to be harsh, but it seems to help. Am I wrong? Should I just be kind, knowing it won't work? Please, I need advice. Pray for my mom-may Allah guide her back to the straight path and grant her wisdom through this trial. Jazakum Allahu khairan for reading.