Lump in the groin area may be Hernia.It may be Inguinal or Femoral hernia
Second possibility is a Lymph
node,which got enlarged due to infection.
Third possibilty may be a Lipoma
,selling arising from fat cells.
Most of them will be diagnosed by Clinical examination.IF there is any doubt,she may be subjected to few investogations like Fine needle aspiration cytology(FNAC) and Ultrasound
scanning of the swelling and surrounding area.
Please consult a Paediatric surgeon and get her examined.
Wish her good luck.