Source of Scorpions

Question: Who is Malinalxochitl's mother?

A mystery! Nobody knows, but there are a few possibilities.

Firstly, Malinalxochitl herself is something of an enigma. She's actually more often said to be Huitzilopochtli's sister than his daughter (we happen to use her as a daughter, but I imagine most games probably don't), and in neither case is her parentage discussed. This is not actually too weird for ladies attached to Huitzilopochtli; Coyolxauhqui, who is typically considered his sister, is also in some variant stories referred to as his mother or aunt. As one of the few Aztec gods with no firm consort or wife, Huitzilopochtli is in an odd limbo when it comes to female relationships; the only truly firm constant is that Coatlicue is always considered his mother, while other females in his stories are always antagonistic and dangerous despite being in some way related to him.

If you consider Malinalxochitl to be Huitzilopochtli's sister, then she'd by definition need to be a daughter of Coatlicue, his only parent. She's never said to be one of the Centzonhuitznahua and has no apparent star-connotations, but she still might be a sibling of theirs, most likely a daughter of Mixcoatl and Coatlicue like everyone else. I've even seen some scholar speculation that, if she were sympathetic toward the deceased Coyolxauhqui and her army, she might be intentionally making Huitzilopochtli's life hard and attempting to steal his people as a form of revenge against him for murdering her siblings. If you roll with that, she'd also be at least a half-sibling of several other gods, most notably Quetzalcoatl. There's much less to go on if you want to run her as Huitzilopochtli's daughter instead of sister; since there's no inkling who her mother might have been in that case, it's probably simplest to consider her an example of an ancient Scion who rose to apotheosis back in the day, and that the forgotten mother was some nameless mortal.

Malinalxochitl's name also turns up in accounts of the Acolhua dynasty of Chichimec nobility, where she is said to be married to a king named Xolotl. Of course, this refers to mortal figures who took on the names of their gods to illustrate their nobility and honor the deities who were their patrons, but if you wanted to mess around with what the scorpion-goddess was up to post-exile, you could always consider her to be the same figure, either as a goddess influencing mortal affairs in Avatar form or a Scion or servant of Malinalxochitl, doing her work in the World.