Some of what wikipedia reports on her:
In the fall of 1814, Grand Duke Nicholas ...and his brother...Michael, visited Berlin. Arrangements were made between the two royal families for Nicholas to marry Princess Charlotte, and on the second visit the following year, Nicholas fell in love with the then seventeen year old Princess Charlotte. The feeling were mutual, "I like him and am sure of being happy with him." She wrote to her brother, "What we have in common is our inner life; let the world do as it pleases, in our hearts we have a world of our own." Hand in hand they wandered over the Postdam country side, and attended the Berlin Court Opera. By the end of his visit, Grand Duke Nicholas and Princess Charlotte were engaged. The wedding would not take place for another two years....On her birthday, July 13, 1817, she and Nicholas were married in the Chapel of the Winter Palace. "...I felt myself very, very happy when our hands joined..." she would later write about her wedding. "With complete confidence and trust, I gave my life into the hands of my Nicholas, and he never once betrayed it.
Weeks after the wedding, Alexandra was pregnant. On April 17, 1818 she gave birth to her first son, the future Alexander II, and the next year she had a daughter, Grand Duchess Maria...In 1820 Alexandra produced a stillborn daughter, her third pregnancy in three years, which brought on a deep depression. Her doctors advised a holiday, and in the autumn of 1820 Nicholas took her to see her family in Berlin, where they remained until the summer of 1821, returning again in the summer of 1824. They did not come back to St. Petersburg until March of 1825 when Alexander I required their presence in Russia....spent her first years in Russia trying to learn the language and customs of her adopted country under the tutelage of the poet Vasily Zhukovsky, whom she characterized as being "too much of a poet to be a good tutor." The Imperial family spoke German and wrote their letters in French, and as a consequence, Alexandra never completely mastered the Russian language. Nicholas and Alexandra were private people who found great pleasure in each other’s company. She wrote in her memoirs of her first years in Russia, "We both were truly happy only when we found ourselves alone in our apartments with me sitting on his knees while he was loving and tender.
Alexandra was tall, slender with a small head of refine features. Her blue eyes were set deep in her head. She had an air of regal majesty. Her quick, light walk was graceful. She was frail, often in poor health. Her voice was hoarse, but she spoke rapidly and with decision.
....was an avid reader and enjoyed music. She was kind and liked privacy and simplicity. She dressed elegantly, with a decided preference for light colors, and collected beautiful jewels. Neither arrogant nor frivolous, Alexandra was not without intelligence and had an excellent memory; her reading was quite extensive; her judgment of men sure, slightly ironical. However, her interests were mostly shallow. She loved to dance and the fantastic world of the Palaces and court balls filled her horizon. She did not worry about knowing the real problems of the Russian people that demanded from its Empress the energy to take care of the needed and the sick.
By 1832 the Nicholas and Alexandra had seven children ...Nicholas I never wavered in his love for his wife, whom he nicknamed “Mouffy”. In 1837, when much of the Winter Palace was destroyed by fire, Nicholas reportedly told an aide-de-camp "Let everything else burn up, only just save for me the small case of letters in my study which my wife wrote to me when she was my betrothed.