I can sort of see BOTH. There is something rather Phoebe like in this character such as the odd almost angled eyeglasses and the color scheme (black hair, dressed mostly in blue). And it’s not like HA characters don’t exist in other bleed comics (Helga is/was Grim and Minnie’s governess, if I recall). But there is a bit of Miyuki there too (at least, going by the sketch that is all of the official art of Miyuki we have)

I really wish we could see her hands, that might give a clue. Unless Miyuki was so committed to her disguise she was willing to amputate the ends of her fingers, I can’t see them fitting in human disguise hands (she might be, I mean unlike Red and Purple, she was apparently committed enough to amputate her thumbs as per Tallest custom)*

Also the fact that she DOESN’T have thumbs should be a bit of an impediment since it would probably mean the disguise thumbs wouldn’t work properly which would be a hindrance in a scientist/doctor disguise (or indeed any persona where she’d have to use her hands a lot)

*I’m assuming that the tendril fingers Tallests have ARE their actual fingers as opposed to prostheses manipulated by their real fingers inside of the gautlets.