Morgan (モーガン Mōgan) is a "self-proclaimed", "so-called genius-type female" and a bit of a mad scientist at times. Apparently, she's an important character, but has no background story. She appears as the 4th boss of Kioh Gyoku, then about 7 years later when Banshiryuu had C74 version release, she appeared as the 5th Extra Stage boss as part of a boss rush.
https://en.touhouwiki.net/wiki/Morgan