Original: Xenia wrote on March 15, 1910 that she could n't understand "... the attitude of Alix and the children to that sinister Grigory (whom they consider to be almost a saint, when in fact he's only a khlyst!)"
Simplified: Xenia wrote on 15 March 1910 that she did not understand "the attitude (behavior) of Alix and the children to that sinister Grigory".