I'm unable to figure out the scientific name of the mushroom she's based upon, and neither was oso from the looks of it.
oso himself calls her "Amanita sp. hamakusagitamagotake" and "Amanita puremuna", the latter in katakana so it may be spelled differently. 'Tamagotake' is the Japanese name for Amanita sect. Caesareae, but hamakusagitamagotake specifically have no scientific name associated with them anywhere that I could find.
oso also mentioned that he previously thought it was a 'Miyamatamagotake', which is Amanita imazekii.
Edit: 浜臭木 (hamakusagi) is Premna japonica, a species of bonsai. Going to tag this character amanita premna for now, though it's not an official scientific name but rather based on the mushroom smelling like hamakusagi.