You must consult an ENT specialist
and get her examined.
If required a repeat biopsy
can be done and if the ENT surgeon feels then an Excision biopsy can be done .
In excision biopsy the whole of the lesion will be removed and sent for Biopsy reporting.
Sometimes the initial biopsy is negative as the lesion in bit inside the mucosa and may be taken from a non representative place .
So it will be better if you get done excision biopsy.
You must hurry up as these tongue lesions are very notorious and grow fast. so it needs to be removed and biopsy done .