The concept of a 'semi-demi goddess' isn't a standard classification in Greek mythology, but if we're talking about figures who straddle the line between mortal and divine, my mind immediately goes to nymphs or minor deities like the Muses. Nymphs, for instance, were nature spirits often considered lesser goddesses—bound to specific places like rivers or forests. They weren't immortal like the Olympians but lived far longer than humans. Then there's someone like Psyche, a mortal who married Eros and was eventually granted immortality. Her story feels like a perfect blend of human vulnerability and divine transformation, especially in 'The Golden Ass.'
Another angle is the demigods, like Hercules or Perseus, born from one divine and one mortal parent. But calling them 'semi-demi' feels a bit off since they're usually just labeled demigods. Maybe the term fits figures with even more diluted divinity, like the descendants of demigods? The mythology is fuzzy on that front, but it's fun to speculate. The Greeks loved their hierarchies, so there's probably some obscure nymph or local spirit that fits this description perfectly.