Answer

In the standard Jain sources I checked, Nilakeshi is not clearly listed as a kshetrapalni or as a yakshi. The name Nīlakeśī is also used for a Jain Tamil minor kāvya / literary work, which suggests that it is not a widely recognized canonical attendant goddess name in mainstream Jain classification. ( jainworld.com)

Explanation

In Jain tradition, yakṣīs are the female attendant deities associated with the Jinas, and Jainpedia gives the standard list of 24 yakṣa-yakṣī pairs. Nilakeshi does not appear in that standard overview. Jainpedia also explains that kṣetra-pālas are guardians of land or temple precincts, and says they live in the lower levels of the upper world of the Jain universe. That classification applies to kṣetra-pālas in general, but I could not verify Nilakeshi under that category from the sources I found. ( jainpedia.org)

Spiritual Understanding

From a Jain perspective, the main focus remains on the Tīrthaṅkaras. Attendant deities such as yakṣas, yakṣīs, and kṣetra-pālas are secondary and can vary by sect, region, or temple tradition. Jainpedia notes that some of these deities have developed independent regional cults, so local usage may differ from the standard canonical lists. ( jainpedia.org)

Takeaway

So the safest Jain answer is: Nilakeshi is not a standard, universally accepted yakshi or kshetrapalni in the mainstream Jain lists I could verify. If the name is being used in a local temple or regional tradition, it may be a local devotional name rather than a canonical classification. ( jainpedia.org)