"it will get better soon" that's great advice from a medic that hasn't even examined the child, grossly irresponsible if you ask me!!
I would certainly take others advice on this and take her to GP or hospital, its always better to err on the side of caution.
Where I work, if we have a resident that has had literally any trauma to the head, we immediately phone a GP for advice, we go through the event with the GP and he will usually ask if we think that we require a visit, usually we will say no but in the case of such a swelling the GP will always attend!
I know I deal with the elderly but we do not take any chances with them, you must not take any chances with your little girl, there are no second chances!
I'm sure Sqad is right, it probably will get better soon, but not a chance I would take.
With any head injury that produces a significant swelling it is aways better to have it checked out, preferably not by Answerbank!!