Will it be flown as a UA flight number? Has your ticket been automatically rewritten as a UA ticket so that you now have a UA fare class? You will want to check whether you get a UA boarding pass for the flight, which would seem definitive to me since within *A, the metal is what matters for mileage accrual, not codeshares or who markets the flight.

You could try phoning or emailing Aegean to ask, but since you already have the ticket and will fly next week, I would be inclined to wait and see how your miles post. If there is an error in your favor, you do not want to risk calling attention to it.

After the miles post, you will see whether you have made *Gold or need more flights on *A.