Also, no matter how awful the Empress's spoken Russian may or may not have been, she was obviously able to read it no problem,a s in her letters to the Tsar she comments sometimes about what is in the papers, and also Alexei wrote to her in Russian. Her aural ability must have been OK too, as the Tsar read to her in Russian, and Orthodox religious books she read would have naturally been in Russian.
I think it has been mentioned before, that people have varying degrees of ability in language (i.e you can speak perfectly fine English, but your written English leaves a lot to be desired, or that you can understand spoken Russian, but your own ability to speak Russian is not so good as your aural comprehension.) I think this may well be the case witht he Romanovs. Presumeably they used English quite a lot as a means of communication - one would hope/expect their spoken and aural capabilities far exceeded (in the case of the children) their written ability.