Should my niece and i be entitled to the disability premuim?

My niece lives with me and her pip was bacdated to july 2017. And i was caliming pip untill november 2017 and we were getting the extra money for the  disability premium on our esa  as we were both recieving pip so in my opinion we should be entitled to the disability premium from july to november as if she had not had it stopped in july then we would have been recieving it untill november when mine was rejected am i right in thinking this or not and if so what should i do ?