Good News! Lakshmi's "growth" was not a tumor, but an abcessed tooth that needs to be removed. The abcess had bulged through the bone on her face, and that was the "growth" I saw. She gets so upset when the vets try to look into her mouth that they cannot unless she is anesthetized. This may be a primary cause of her current mouth pain.
I just hope she survives the dentistry. She has a grade 3 heart murmur, and of course cancer and stomatitis.