my budgie used to look in the mirror, now she taps the mirror with her beak. Is she angry or what?

she is insecure, dress her up and maybe give her a hat and she should feel better about herself

Playing! An angry budgie gives a quick downward peck and often a squawk, but repeated tapping, sometimes with clicking noises, is play/courtship. One of my budgies likes to tap-play with my fingernail lol.

She's just playing.

It just thinks it's another bird and birds touch each others beaks.

Other than magpies, birds are not aware that the refelction in the mirror is themself. She's threatened and attacking the "other" bird. Sometimes the bird sees the "other" as a friend.

It's just a sign of playfulness and wanting to get to know the "other" bird she sees.

She can't comprehend mirrors and looking at herself.