Edit

Macha turning into a mermaid is again a legend, thus the crest of the mermaid for the city of Emain Macha itself.

The Music Guy in Emain Macha, Nele, sings a song comparing Aer's beauty to that of Macha just to please Aer (no, he probably does not know macha's beauty for sure)

Just fyi, this particular discussion has already finished so there was really no reason to reply (It took place a year and a half ago if you didn't notice). The piece of trivia comparing Macha to Aer has since been removed on both of their pages.