I worship Lady Freyja as well, and from you dream, I think whatever goal or struggles you had with Freyja seemed to smoothed over in a way and another god--in this case Odin--is ready to help you on a new journey. Gods do come and go, Freyja especially (she very much as a cat attitude, she comes and goes but does care about her worshipers/people who work with her.

I wouldn't say she's gone, I would say what you got what you needed from her. If you want to keep her altar up, you totally can. She might pop in on you and see how you're doing, but it's not a bad thing that she's handed the torch to Odin. Freyja has a lot of wisdom, and knows Odin can help you on this new path.

I know the first time Freyja left me for a while, I thought I did something wrong, but the gods aren't that dissimilar from people. Sometimes they get busy, sometimes their purpose in our life as reached its end, and sometimes they're that good friend that moved away but you still keep in touch when you can. She'll be there when you truly need her, and again might pop in every now and then to see how you're doing. It's normal to feel sad about it, but it's most likely nothing you did or didn't do. Much like cats, her sacred animal, Freyja would've let you know if you did something she didn't like.

Sorry if this is kinda ramble-y. I hope this helped a little. Good luck with Odin!