My14 year old friend, wants to know how can she tell how big her boobs will grow? also how can she tell, if they have stoped growing?

Wait and see: I don't know any reliable way for your friend to tell, though seeing the breast size of her mother, aunts ; older sisters may give a general idea. I also don't know a way to tell if they have stopped growing but most women's breasts continue to grow well past age 14- jus compare the average breast size of 14 year-olds to women in their twenties to see that they tend to keep growing!