The only question of Aspasia's status was whether Constantine would recognize the marriage as being valid.
The issue came up at some point before it was known what type of wedding (civil or religious ceremony) had taken place, since it was kept secret. According to the book by Dr A Zaoussis, the wedding took place in an Athenian house, the Archimandrite of the Palace officiated and politician Mr Christos Zalokostas was the best man. In the Greek Orthodox rite, divorce can be granted but marriages do not and cannot get anulled if performed by a member of the clergy. The Orthodox scripta dictate,
"Those that God united, no man shall split". Thus, no power on earth has authority to annull (ie invalidate) a properly conducted religious Orthodox ceremony.
At the time, the house laws required princes of the blood to marry equally and with consent from The King. Since Aspasia married a reigning King, she obviously had permission at the time.
It goes without saying!!! You are absolutely right here, but the house laws issue is a separate one and pertains only to dynastic matters, titles etc. The marriage, per se, was legal simply because in Greece the Church is a Branch of the State and the Clergy are civil servants.
There was then a question of whether the marriage itself was legal in Greece. The courts eventually ruled it was a legal marriage and the King's decree then followed.........
Technically, she was, albeit briefly, Queen Aspasia of the Hellenes......
In the end, the "legality" issue had nothing to do with the validity of the marriage or the house rules (which could easily be overcome by letters patent etc). The problem, I believe, was that the Greek Law did not permit the granting of titles of nobility to Greek citizens. Thus, a Greek citizen, albeit allowed to marry a prince [eg Greek commoner M Karella who married prince Michael] or even the king [eg Aspasia Manos], could not become a noble person or be granted titles etc.
It would be extremely interesting to see how the then scholars of Constitutional Law overcame the obstacle. I guess there were possible ways. For instance, arguing that the titles of the members of the royal family are not titles of nobility. Once, then, she became the spouse of the king, house rules could be applied at the discretion of the monarch.