Mallow's mother is a minor character who appears in Sun & Moon - Ultra Legends.
Pokémon the Series: Sun & Moon
Little is known about Mallow's mother, except that she was the one who caught Bounsweet for her daughter. Unfortunately afterwards, it was presumed that she passed away by an unknown illness when Mallow was around 2–3 years old. She briefly returns as a spirit to see her now grown up daughter and newly evolved Tsareena.