There is no way that the Mono Mix is just a different take. That’s a whole new woman. Considering the rest of the audio errors the mix corrects, I bet they decided the original voice was just a bit off-sounding for her and decided to redub her entirely.
That makes me wonder something else… Considering the sheer amount of new ADR in the Mono Mix, is it at all possible that there was another recording session that took place after release?