A few points are worth keeping in mind:
Emmerich herself did not publish these texts.
Most of the famous works attributed to her were written down and edited by Clemens Brentano. The reliability of some passages has long been debated, and the Vatican explicitly separated her personal sanctity from the authenticity of all the published visionary material.
Nineteenth-century mystical language often differs from modern terminology.
When Emmerich speaks of stars, planets, celestial spheres, angelic hierarchies, or spiritual influences, she is generally operating within a symbolic and spiritual cosmology rather than describing extraterrestrial beings in the modern sense.
Traditional Catholic interpretation.
A traditional Catholic reading would normally understand any genuine reference to spirits connected with planets as referring to angels, demons, or symbolic spiritual influences—not literal inhabitants of other planets. The Church has never taught the existence of “inter-planetary spirits” as a distinct category of beings.
If you have a specific quote containing the phrase “Mischievous Inter-Planetary Spirits,” send it to me.

Thank you for all your information Wulfram Elendur Magladhur. The sentence of The Mischievous Inter-Planetary Spirits is mentioned in one of the in one of the two of two volumes of the Life & Revelations of Anne Catherine Emmerich by the very Reverend Carl E. Schmoger, C.SS.R. ~ As you possibly know she talks about 'A New Church under the influence of Planetary Spirits'. Volume two, pages 57 - 252 - 253 and 254. Perhaps if she had said 'Fallen Angels' it may have been understood a little better! ~