Sorry, but 'she is rarely going out' is not proper English. You can use 'she is going out' as the present continuous tense for the act of doing so, and 'she rarely goes out' as the simple present tense for the frequency with which she does so, but you cannot mix them Basically, the present continuous is only for an action occuring at that moment in time.
I first tried, "She rarely gets out", which in my opinion is the same as "She rarely goes out". Duo accepts the latter, but not the former. It IS a different word as far as translations go, but it's not incorrect to say it this way in English. Should it be accepted, do you think?