Tell me about the changes a girl goes through in puberty?

Multiple changes: breasts swell, labia swell, pubic hair grows, serum estradiol and progesterone increase phasically

During puberty: girls develop breasts, hair under the arms (axillary hair), hair in the vaginal area, and then get their period. They also have their biggest growth spurts during the year prior to getting the first period, and grow a little bit over the 2 years after.