Hi,
How is your girlfriend? Diagnosis of headaches caused by tumor can be done with imaging studies such as CT scan or MRI. Tumor headaches present with pain that progressively worsens, projectile vomiting, possible visual disturbances speech or personality changes; problems with equilibrium, gait, or coordination; and even seizures. To rule this out, it is best that further evaluation be done including the imaging study and blood tests. Take care and do keep us posted.
Encourage your girlfiend to follow her Doctor's advice and if she dosen't have health care insurance to obtain it.