Modena, I have read two of Oman's biographies, those of Henrietta Maria and Elizabeth of Bohemia. In my opinion, Oman ignores and minimizes failures and mistakes of both of her subjects to make them look better.
For example, in her biography of Henrietta, Oman spends just a few pages on Henrietta's political activities during 1643-4, and downplays her actions. During that time, Henrietta conspired with some of the courtiers to remove Prince Rupert, Charles's best general, from his command, since he failed to suck up to her. Henrietta wasted time negotiating with the Pope and with other Catholic foreign powers who had shown all too clearly that they were not interested in helping her or her husband. She discouraged Charles from listening to warnings from the Marquis of Montrose that the Scottish army was negotiating with Parliament and would soon be on the move. She demanded that Charles make an incompetent schemer, Lord Digby, his Secretary of State. And so forth and so on....
Oman, who goes into great detail about other times in Henrietta's life, glibly sums Henrietta's actions during the Civil War up, leaving most of her monkey business out. Oman then moves forward to the birth of Minette and Henrietta's flight to France, dwelling long and lovingly on the various illnesses Henrietta suffered from in 1644-5.
Prince Lieven, not everyone thought Mary of Orange was good-looking. Elizabeth of Bohemia's granddaughter Liselotte paid a call on Mary with her grandmother while on a visit to The Hague as child. On her arrival at Mary's court, Liselotte asked a little boy who the woman with the "furious nose" was. The boy, the future William III, told her that it was his mother, Mary of Orange; far from being offended, he thought Liselotte was pretty funny. William and Liselotte had a good time playing together. When told that it was time to go, Liselotte rushed up to Mary, yanked on her dress, bobbed a curtsey, and followed her grandmother out, imitating the Winter Queen's walk and taking precedence over Mary. Liselotte's Aunt Sophia, who had boycotted the call, laughed when she heard about this and told Liselotte that she had revenged the family on "that haughty princess."