If the girl can handle her man and herself
but if she can't because she has thin body or because she is weak then no rush until she is ready for marriage

about the age matter, she could be 10 years old and be able to handle it
and she could be 15 but she can't handle because of weak body or sickness etc
and if that is the case then her guardian look into her case
and not allow her to marry until she is capable of handling the marriage

Fatwa by sheikh Ibn baz