Manuela sings the Song of the Nabateans in jp? Even more implication of it being Rhea who inspired her to sing, and it was already heavily implied.
Her lyrics are different, but it's the same tune (albeit, not the part Rhea is humming when she's singing her lullaby).
Just like the Enbarr/Gritnea and Saias is Arvis's kid, it is not said so it is not canon, but Manuela, as you pointed out, is heavily implied to have heard Rhea sing, and in turn, Rhea inspired her to sing.
Which is why, imo, Manu joining SB or being part of the Imperial forces in AM is sad - the known Nabateans have inspired her/can become her friends, but their ears being pointy means that in Nopes, she will always fight against them.
It's even more baffling because in Nopes, we learn more about Mittelfrank and we even learn that one of their plays is about some sort of interspecies romance between a human and what is implied to be a Nabatean...
Manuela could have meaningful interactions with Nabateans, and know they are not evil because of their ears - but Nopes being what it is, Manu was eggtivated to sell even more Hresvelg Tea.
Pour one (or pour the first one) for Casagranda.