Godgift, I'm so sorry you and your daughter are dealing with this. I know I would be a little frightened.
My suggestion is to take her to the doctor to be checked out. A mammogram would probably be ordered. It could only be a lymph node or a fibrous nodule but you want to be safe than sorry. This is what I would do if she were my daughter. It's just good sense.
I think it's pretty rare for such a young female to have breast cancer so try not to be overly worried. But I definitely would have her checked out. Hope this helps.