Is a daughter who died by drowning at the age of 8 considered a martyr? Is she in Paradise? And does she feel her mother’s patience?

Patience in the calamity of losing a Muslim daughter by drowning is commendable. Drowning is martyrdom, and Muslim children are in Paradise by consensus. Your daughter died young by drowning, and this is good news; she may intercede for her parents. The creed of Ahl al-Sunnah wal-Jama'ah does not definitively affirm Paradise for anyone except with a text [from revelation], so we hope for her Paradise but do not definitively affirm it. There is no evidence that the deceased feel the state of the living, and you should supplicate for your daughter and have good thoughts of Allah.