Why is my budgie suddenly afraid of everything?

[Blackberry Sage]

About a week ago I found a malnourished and abandoned budgie parakeet outside my house. I brought her inside and put her in the empty 55 gallon fishtank I was setting up for some new fish I planned on getting, put sticks and bird food and water in there, and she was fine.

She would come out and sit on everyone's shoulders and loved to be petted and she would nuzzle my cheeks and nibble my ears. And she was very very quiet. Never made a peep.

Then my dad brought home a small birdcage. Only 15x15 inches which I know is too small, but I had to put her in it anyway because we had to finish setting up the fishtank.

And now that she has this tiny cage, she doesn't want to come out of it. She freaks out when anyone comes near the cage, and even if I leave the front open she won't come out. And she tweets quite a bit now, pretty much every time someone comes into the room.

Is she just really attached to the cage, or did I do something wrong? She hates me now and its sad.