1. Are you at your mother's right now or are you home?
2. Are you at your mother's or (are you) at home right now?
I would include the 'right' in the second sentence.
The words in brackets could be omitted. In the first part of the sentence, you have said, 'are you at' and then you use 'or' which means a choice, 'at mother's', or 'at home' - Are you at your mother's or at home right now?
Student or Learner