Missing My Mother, Feeling Her Peace, and Trying to Make Sense of It Islamically

Assalamu Alaikum. I've been holding onto a lot of sadness, and I'm reaching out for some Islamic guidance and maybe stories from others who've been in my shoes. My mother passed away not long ago. She finished her cancer treatments, and we really thought she was getting better. Then, out of nowhere, she got septic shock, and despite the doctors' efforts, she left us. Seeing her go through that broke my heart in ways I can't describe. For almost two months before she died, I prayed Tahajjud every single night, begging Allah to heal her, and I fasted on the Day of Arafah too, pouring my heart into dua for her recovery. I had such strong faith that Allah would answer me the way I wanted. When she still passed, I was crushed. I know Allah's plan is always perfect, but it's hard to deal with the hope I had and what actually happened without feeling guilty about those thoughts. Since then, something strange has been happening. Sometimes I get this wave of calm, like she's still around comforting me. I don't see or hear her-it's more like that safe, warm feeling I'd get when she was right there with me. It gives me a bit of peace. But then, other moments, the weight of losing her hits me hard, and it's just agony. I miss her terribly. Islamically, how do I make sense of this? Is it just grief playing tricks on me, or is there something in our faith about feeling a loved one's presence after death? How did you cope with losing a parent while still holding onto sabr and trust in Allah? What kept you going in those early months? Any specific duas, verses, or thoughts that brought you real comfort? Please, make dua for my mom-that Allah forgives her, showers her with mercy, brightens and widens her grave, accepts all her good deeds, raises her to the highest place in Jannah, and reunites us in Jannat al-Firdaws.