Is my being alone with my niece considered a forbidden khalwa?

It is forbidden to be alone with a non-mahram woman, as the Messenger of Allah, may Allah bless him and grant him peace, said: "No man should be alone with a woman unless there is a mahram with her." As for being alone with one's niece, it is permissible because she is a mahram, unless there is suspicion or fear of temptation, in which case it is not permissible to be alone with her or to look at her with lust.