Hello! For things that are wisp-level and lingering, no—being unable to retain a shape or have much of an identity is intrinsic to what they are.

For stronger incorporeal spirits more on the level of the native Horror spell, they can take vague and uncomplicated shapes evocative of (for example, in canon) an enormous skull or vague swirling glimpses of horrors, but until we reach spirits too strong to be used without native summoning rituals and so on, which would be outside of Priest's reach, they'll be shaping themselves based on the person they're trying to frighten, not the fears/orders of the person who uses them. So with that in mind, if she brings one in, while its focus is on her, its shape can be something familiar to her, but the precise shape would depend on the type of spirit and what emotion it's attempting to provoke from her rather than necessarily what she is expecting.