They are right, there likely is something 'in her brain' that causes this. My daughters walk on their tip toes as do I if I don't consciously think about it. It's related to neurological issues, such as sensory integration dysfunction (does she seem to be particularly sensitive to sound or touch or get over stimulated or is she always moving/going/running into things?) Asperger Syndrome or Autism Spectrum Disorder are also common to find with toe walkers. Some have said their very gifted children are tow walkers, so perhaps they have AS but are so high functioning all anyone notices is the toe walking and their brilliance!
No one really knows exactly why it happens. Surgery isn't going to help right now, but I did meet one adult who needed surgery because as she grew older her legs never grew appropriately. an occupational therapist who helps with walking or with sensory integration disorder might be of some great help. Apparently some use something called Piedro Boots
http://www.asdfriendly.org/board/index.php?showtopic=8626
http://www.asdfriendly.org/board/index.php?showtopic=9966
Please feel free to PM me.
S.