Why didn’t you just give her water

Just some context: last night my mom and sister had an argument. My mom thought that my sister was using her nail clipper to commit self harm, when my sister was really just trying to take a lash or whatever out of her arm. She started crying and went to bed and that was the last time I saw her. I went to bed a while after that, a hour later my mom woke me to rush her to the hospital sense she killed herself while we were sleeping, but it was far to late.