My budgie pair don't have a mirror, and I know it's perfectly normal for them to talk to mirrors. But I'm not talking about mirrors, or any reflective surfaces they may see as another bird.
One of my budgies likes talking to the inanimate objects of the cage, like perches, toys, food clips, and the cuttle fish bone. I could be wrong, but it definitely looked like he's talking to the objects and not his cage-mate.
He presses his face right against the object and talks to it, sometimes kissing/pecking it. Then when his cage-mate tries to get his attention, or interferes in any way, he tells him to go away.
Usually they enjoy each others company, but the budgie that's talking to inanimate objects is a bit of a bully.
One of my birds does this all the time, he is a real goofball. When he is out of the cage he loves to talk to the cage itself, he sits on top of the cage and chats with the corner of the cage He talks to his kabobs and other toys and millet clips. Totally normal