In China, Thailand, Singapore and Malaysia, legend has it that a banana tree that dies before its first bloom will become an apparition in form of a beautiful young maiden, haunting those who wander too close to her tree. This spirit is usually harmless and she will even grant favors should her tree be located and bound with a specific ritual, but once she falls in love, it is said that she will pursue the object of her affections with psychotic devotion, murdering any potential love interest with the supernatural powers at her disposal in hopes of her beloved choosing her over the potential rival. If the lover in question is stupid enough to cheat on her, the result is a swift death for all parties involved. Those who play Ragnarok Online will recall such a spirit as Lady Tanee, the boss monster of the Ayothaya Dungeon. Ayothaya is themed after Thailand, and indeed such banana tree ghosts are called Nang Tanee in Thai (and Ba Jiao Gui in Chinese, as an aside.)
Long story short, if a banana tree dies before giving fruit, she becomes a yandere little girl. As a Touhou, she gets two unopened banana blossoms on her head as her head accessory, since the main reason that she's a ghost is her long-standing grudge over dying before her first bloom. She is rather cheerful and tries to pass off as a nature spirit, but since she's just a vengeful ghost, the fresh banana leaves that she uses to decorate her skirt quickly shrivel and die in her presence, so she needs to replace them often.
Needless to say, she ejaculates banana juice, and is most likely insane enough to use her vaginal secretions to flavor the dishes she prepares for the lucky little girl who steals her heart.