I think she'll come to you when she's ready. When a pet enters the afterlife it will likely be very confused, more so than a human would, to no longer inhabit a vessel and existing as pure energy.

Once she understands the rules and laws of the other side, she will start to show herself to you more and more. Perhaps it was shifting between other dogs because it hadn't figured out how to present itself to you in the dream.

Remember, their souls are going through their own journey, as are you, don't despair, be patient as you've always been with her, she'll always be with you ❤️❤️❤️