You might ask her more directly if she would like family to come now (perhaps in the context of "would you like to see...") She may be waiting for them before she feels ready to go even while she denies that she wants them to see her this way. Also, she may feel that you and/or your aunt in particular are anxious about her passing and I would reassure her that you wish her well and will ensure that others' visits are on her terms. I would say anything you want to say to her and encourage your family likewise, though whatever communication means is necessary. A one-way conversation, where she just listens, can be very comforting. You can read her e-mails, show her pictures, whatever reminds her of how she will live on through others.
The question now may be less "how do you know when" but "how do you help" her journey, which will be easier with whom/what she values at her side and what needs to be said, said. The more peace you find within yourselves, Amanda, the more she will take with her.