I traced that picture back to the original artists Deviant Art page where they give their sources as the Florentine Codex and Clavijero's History of Mexico. I'm not sure what exactly they were citing from Clavijero, but specifically on the topic of Sahagun and ahuianime the old friar is very clear in the Florentine Codex that these women were not esteemed; less geisha, more streetwalker.

For instance, his summary of an ahuiani in Book 10 is:

in auiiani, ca cioatlaueliloc, inacaio ic mauiltiani, nacanamacac, nanacanamacac, ichpuchtlaueliloc, ilamatlaueliloc, tlaoanq̃, xocomicqui, tequixocomicqui, tequitlaoanqui, iellelacic, tlacamicqui, suchimicqui, tlaaltilli, teumicqui, teupoliuhqui, miccatzintli

The carnal woman is an evil woman who finds pleasure in her body; who sells her body—repeatedly sells her body; an evil young woman [or] an evil old woman, besotted, drunk—very drunk, much besotted; dejected, perverse; [like] a sacrificial victim, a bathed slave, a captive; full of affliction, mortal.

Molina is much more terse in his Nahuatl-Castilian grammar, translating the word simply as "puta, o mala muger." English translations (such as Anderson and Dibble) have used terms like "harlot," "carnal woman," or "pleasure girl," though Kartunnen apparently gave the meaning as "courtesan," which may have introduced some confusion to the meaning.

Clendinnen, in (1991) Aztecs: An Interpretation notes the term "ahuiani" actually derives from "ahuiya," which Molina translates as " tener lo necessario y estar contento" and Kartunnen as "to be happy, content." The term "pleasure girls" or maybe even the old-timey "good time girls" might therefore be a fitting epithet. Clendinnen argues that this is too simplistic an interpretation and one fraught with the moralizing of the Christian friars who recorded much of what we know about pre-Hispanic Nahua life. Instead, she suggests that these translation removed from the social context of the ahuianime misses the subtext of "contentment" which in her opinion is "self-indulgence, loose behavior, waste."

Whereas a dry and chaste Spanish friar might be, um... content, to write off the ahuianime as mere prostitutes and a blight upon proper society, Clendinnen prefers to see them as enmeshed in society. They were neither a virtue nor a vice (though definitely shaded towards the latter), as Nahua attitudes towards sexuality did not map well onto the strict dichotomy of Chistianity. You might be interested in my prior comment about Tlazolteotl and the concept of sin, but the main point here is that the Nahuas accepted natural instincts like sexual lust as just that, natural instincts. It was only when someone overindulged in pleasurable acts -- be they sex or gluttony -- that these innate parts of human life became a problem. To paraphrase a famous passage on Nahua philosophy, the proper life was seen as a narrow, jagged mountain path, with steep, slippery slopes on either side; it required discipline and dedication to navigate successfully.

A poem/song from the Cantares Mexicanos is illustrative of the ideas above. Attributed to Tlaltecatzin, a ruler of Cuauhchinanco, Leon-Portilla interprets the work as the nobleman having a conversation with an ahuiani he spotted in the city (or at least having a conversation with himself about the woman). It's a classic example of the near universal genre of an elite man spotting a lower class woman who he deprecates and objectifies, but also fiercely desires. Ultimately though, he decides he has important elite-man things to do and continues on his way. In an early part though, the writer gushes over the ahuiani. From Leon-Portilla's translation:

el florido cacao está espumoso,

la bebida que con flores embriaga.

Yo tengo anhelo,

lo saborea mi corazón,

se embriaga mi corazón,

en verdad mi corazón lo sabe:

¡Ave roja de cuello de hule!,

fresca y ardorosa,

luces tu guirnalda de flores.

¡Oh madre!

Dulce, sabrosa mujer,

preciosa flor de maíz tostado

Whoa momma, indeed! This is a man enraptured by the sensuality of a woman, but he puts such thoughts aside and denies the ephemerality of the pleasure she offers.

Aquí tú has venido,

frente a los príncipes,

tú, maravillosa criatura,

nvitas al placer.

Sobre la estera de plumas amarillas y azules

aquí estás erguida.

Preciosa flor de maíz tostado,

sólo te prestas,

serás abandonada,

tendrás que irte,

quedarás descarnada.

And finally we come to his self-admonishment and reminding himself of the dangers of unchecked indulgence.

Si mi corazón lo gustara,

mi vida se embriagaría.

Cada uno está aquí,

sobre la tierra,

vosotros señores, mis príncipes,

si mi corazón lo gustara,

se embriagaría.

Yo sólo me aflijo,

digo:

que no vaya yo

al lugar de los descarnados.

Mi vida es cosa preciosa.

I want to bring specific attention to that penultimate line in the quote, about the "place of the emaciated." Nahuas envisioned male sexual energy as somewhat finite, and therefore it was unwise to spend their precious bodily fluids freely, lest they dry out and grow weak. Female sexuality had no such limitations though, and there's a famous story of two older women brought to judgement for their proclivities with a couple of young priests. Nezahualcoyotl, presiding over the court, asked them, "are you not satiated, as old as you are?" to which the women replied with a hearty rebuttal, saying:

you men, you are sluggish, you are depleted... it is all gone. There is no more... but we who are women, we are not the sluggish ones. In us there is a cave, a gorge, who's only function is to await that which is given, whose only function is to receive.

Putting aside the patriarchal assumptions of female genitalia as built only "to receive," that is an unapologetic proclamation of women's sexuality. The Aztecs, however, were a patriarchal society and while they did not deny the sexual desires of women, they saw it through the lens of the danger it posed to young men if they discovered all the hot MILFs in their altepetl. They might waste their vital energy in debauchery, rather than focusing it on the proper activity of a man: warfare.