"Les Derniers Années de la Cour de Tzarskoe Selo", Spiridovitch, Payot, Paris. My personal translation from the original French:
The Year 1914
The fact that the two oldest Grand Duchesses, Olga and Tatiana Nicholaiovna, had reached their age of majority, gave rise to the idea in the heads of some of diplomats that one of them should be married to the Crown Prince of Rumania.
The father and son had both come to Petersburg at the beginning of that year; however the young man was badly brought up and little cultivated, and had a mop of uncombed hair, and so greatly displeased not only the Grand Duchesses, but the Empress herself.
After their departure, they teased Olga quite a lot about that subject, and this always put her in a bad mood.
The rumors about an imminent marriage of Grand Duchess Olga were firmly going around in the Crimea, after it was learned that Their Majesties were going to go to Rumania.
Olga Nicholaiovna would not be separated from her family. "I shall never leave Russia" she said to one of those near to her. "I shall never marry anyone who is not Orthodox" she declared that summer to one of the Officers of the Standardt.
There were not just mere phrases. One needed only look here in the face to see that she breathed sincerity, look in her clear and pure eyes to understand that as she pronounced these words, that the was saying them with the most intimate and sincere conviction, that her decision in these things was most firm.
With all her being, with all her thoughts, Olga Nicholaiovna was a young Russian girl. More than that, he had realized the ideal of the young Russian girls and she was quite conscious of it.
The persons in the Tsar's entourage had heard for themselves all of the rumors about the eventual marriage, and everyone was of the opinion that such a thing would not do for the daughter of a Tsar of Russia. Everyone wished to see the Grand Duchesses marry Russians and stay in Russia.
... It was most unpleasant for us to listen to the absurd conversations of the Rumanians about the occasion of the visit of the Russian sovereigns. Our diplomat, who had done much to obtain a transfer to this post, committed a misstep which was rather humiliating for the Imperial Family. He had listened to the last idiot in Constanza who had told him that the Tsar was bringing his daughters to Rumania to marry them there. Everyone among us was furious at our diplomats and were even more vexed at those storytellers who were repeating that story at that time about the marriage of one of our Grand Duchesses to the son of the Crown Prince, even though the matter had been definitely resolved, and was negative. All those who knew the truth, however, were glad for it.