what could make a 12m so angry?

my baby is 12m 2w but she is always angry to something, and i couldn't figure out what is that something.

i understand she is frustrated when i couldn't understand her baby's language but sometimes her mood just changes too fast.

for example: when i read to her, half way, she just hit the book to the floor. baby will start to cry while trying to pick up the book. she will smile back when the reading is resumed but after a page or so, she could get upset again and hit the book.

she used to hit me and i have managed to tell her that's wrong and she can only touch gently. now she choose to hit food tray, wall or carpet. she seems really angry with something. normally i will offer hugs but she will get even more upset and push me away.

thank you for replying.