neelA of KrushNa avtaar is different from neelA of vishNu-vaikuNTa
neelA of vishNu-vaikuNTa is connected to three steps of vishNu as described in chapter 227 of padma puraaN :
" The pervading with his third step is done in the highest abode. One step of him was here also. His vibhUti with the third step is perpetual, (while) the step (on the earth) is non-perpetual. "
" This nArAyaṇI, the mother of the world, is the resort of the entire world. The entire immobile and mobile world has resorted to (i.e. depends upon) her glance. The existence and the dissolution of the world is due to her opening and closing (her) eyes. This great lakshmI is the first of all. She has three constituents (viz. sattva, rajas and tamas). She is the greatest goddess. She of a visible and invisible form, remains after having pervaded everything. The great goddess having seen the entire universe void, filled that entire (universe) with her own lustre. That lakshmI is the Earth only, well-known as goddess neelA. Being the support of the world, she has resorted to the form of the earth. She herself would be of the form of neelA due to her liquid form of the nature of water etc. She has obtained the form of lakshmI. She is of the nature of wealth and speech. Thus, she, the goddess of the world, has resorted to vishNu. O you of an auspicious face, all the varieties of knowledge would be (i.e. are) her forms. "