I noticed a tender grape sized ball in my upper thigh area (near groin). I am a 19 year old female. Is it possible that this may be a femoral hernia?

Unlikely. If you can feel a distinct size, like a grape, it retains the same size no matter how you push on it , the chance of it being a hernia is remote.Most of these peanut to grape sized structures are benign lymph notes that are often noticed in the fold of the groin.
Yes. Another cause is an enlarged lymph node. Sometimes it is difficult to tell, even for experienced surgeons. An imaging study, such as ultasound or ct scan, can help distinguish between the two. Femoral hernias can contain viscera, such as intestine, and lead to incarceration and strangulation. Lymph nodes can become enlarged from infection, inflammation, or malignancy. You need to see a doctor.