Hi and thanks for the query,
Its a good sign there is neither no pain nor trauma. Generally in young women, breast lumps are generally non cancerous and responsive to hormonal
changes in the female reproductive cycle. These lump are called fibroadenomas of the breast.
A breast ultrasound
is indicated to characterize the lump and exclude other rare diagnostic possibilities. I suggest she meets a gynecologist for appropriate care and advice.
Thanks and best regards,