There is nothing selfish in Alexandra's attitude. She reacted and acted as a loving mother: a mother who is worried about the destinity of her daughter and a woman in ther 40's who see that time has gone and she do not have any little babies any more. Is is a normal feminine reaction. As parents of a almost 18 years old GD and a 16 years old younger girl NIcolas and Alexandra, in 1913-14 do their best: in Livadia, On and TN attended multiples socials events, balls, parties, family meetings. In 1914 NII and AF started to search a suitable fiancé. Nothing came out, but it is absolutly clear that without the war they would have carry one and found one day, the best for their daughter.
Could the GD marry during the war? I don't think so. They were not in a hurry. Olga and Tatiana were young enough to wait and they did not yet have found a fiancé. Alexandra insist on effort for the war: no new dresses, nursing... She surely would not organize a big beautiful weeding when the whole nation was involved in such a terrible war. Remember this page of Chebotareva's diary: one day of january 1917, Olga Nicholaevna was especially sad and Valentina Ivanovna asked her why and is her mood related to the visit of Carol of ROmania. Olga answered: "O no; there is no danger at war time". That 's clear enough.
At the same time, the visit of Carol proved the 2 families did not renounce to their idea. THe visit had political and military purpose, but according to Spiridovich the prince came also with personnal purpose. According to the same Spiridovitch, Carol complained to his aunt Victoria he could not see Olga in particular to speak with her. By the way, the only time when Carol could have ask for Maria's hand, if only this happened (I am not sure) was this 1917's visit.
Well, dear all, don't you think we are discussing the same old things again and again, without adding anything new??