A figure who exists to be sent away is awkward for a system that has to be complete, and the later tradition built exactly such a system. The dikpalas are the guardians of the directions, one to each quarter and intermediate quarter, and a temple, a house plan or a ritual diagram assigns every one of them a position. Nirriti gets the south west. That is a promotion in one sense and a demotion in another: the inauspicious power acquires an office, a fixed place in the architecture and a form the prescriptive texts describe, and at the same time stops being the thing the hymns were frightened of and becomes a slot on a compass rose.
Two things shift in the transfer. The first is gender. The Vedic Nirriti is female without ambiguity. In much of the later directional and architectural material the guardian of the south west is treated as male, and the associated class of beings, the Nairritas, takes its name from the same root. The atlas records the Vedic gender as attested and the later reading as a genuine divergence rather than an error, because both are in use.
The second is what she is for. In jyotisha, Nirriti presides over Mula, the nakshatra at the root of the sky, and a system that has to say something useful about every mansion has to say something useful about a mansion ruled by dissolution. What it says is that endings clear ground, which is a reading the Vedic material would not have recognised. That is not a corruption. It is what happens when a power that a ritual tradition handled by aversion is handed to an interpretive tradition that has to produce a meaning for it.