Not even close with the questions lol.

First of all, va and sa strictly mean yes and no (or no and yes), asking them to use the words to mean something else means you are no longer asking a true yes or no question. The questions must be answerable using yes or no to MEAN yes or no. You might be able to USE someone's answers to get more than affirmation or negation, but they have to be able to answer by simply using affirming or negating terms for the question to be considered yes or no.

If you asked any of the three goddesses if they were Aletheia, both Aletheia and Apate would say yes. Eris would have a 50% chance of saying yes (if she chooses to lie). If you asked if they were Apate, both Aletheia and Apate would say no, and Eris would have only a 50% chance of saying no (assuming she chose to tell the truth). Each of three Goddesses would be able to give the same answer to those questions, so you wouldn't be able to distinguish them that way.

EDIT: If you just meant asking them if they were a Goddess in general rather than a specific Goddess, you would still get one yes, one no, and one random answer with no way to distinguish them. You would need at least one question to translate the terms, the second to begin your process of narrowing it down to two possible candidates for Eris, the third to finish narrowing it down to two, and then being left with a 50/50 guess to finish the job.

Where you WERE on the right track however is in how you simplified the problem. With only a truth teller and a liar left, you can finish in one question, my solution was also to eliminate Eris within two questions. And the hint which I will now provide is this. At the end of my solution, it is still possible that I will not know what their words mean.