Any tumor near the optic nerve (which could be a pituitary tumor) is inoperable since they cannot risk cutting the optic nerve. Often though they do surgery first to debulk as radiation takes months to years to take effect.
It may have been a large, non-functioning pituitary tumor? But still, they would have done testing in that case at a competent practice. If it is pituitary, and this is speculation as it could be pineal or otherwise, she should need replacement hormones.
The brain tumor is near the optic nerve. The information I am able to get from her is very limited.
They can tell cancer in the scans from the shape of the lesions - basically smooth lesions are likely benign and ragged edges are likely not.
They should have given her a diagnosis of some sort in order to have given her radiation so they had to have determined the type of tumor - so it may be a glioma of some sort (I am purely guessing).
It may be that they did not biopsy due to risk due to location, which is why they also opted not to do surgery. You did not note size, location of the tumor.
Do you have a copy of the MRI or CT reports?