A
minor who became betrothed without the knowledge of her father requires
a Get before she can marry another man, for the eventuality that her
father has agreed to her betrothal and it became valid. She also
requires "Refusal", a procedure where the minor says to her husband in
court "I do not want you anymore" in case her father has not agreed.
A
certain man betrothed a minor by giving her a bundle of vegetables in
the marketplace. Here we are not concerned that the father may
acquiesce, because betrothal was not done honorably.