Your friends breasts will develop according to her genetics make-up. Breasts grow because at puberty, your body releases hormones that cause hair to grow 'Down there," arm pits , legs etc, These hormones also cause breast development and curves to form. It's her body clock, that will cause things to happen according to her genes.

The is nothing wrong with tiny breasts, they are quite beautiful.

It depends. It could be her genectics. Nobody can just be like, " you're boobs will grow...NOW." lol but anyway there is a possiblity they will come before. :)

ya, thats when they develop the most