Skull Metastasis and Meningioma en plaque - Question

Hello
My Mom was diagnosed with breast cancer 2 Month Ago.
The doctors performed a biopsy and found that she did not had DCIS type in the left breast and a papillome in the right one.
She decided to be safe to perform a modified radical mastectomy on both breasts.
Now after they have dissected the her breast the pathologist concluded that the cancer has mutated and became an invasive breast cancer, it tested negative for the HER2 and it tested negative (no cancer) in the lymph nodes.
But they said that it was too close to the chest wall (1.5 millimeters) so they decided only three weeks of radiation of the chest wall.
One week before the surgery(which was performed a month ago) they scanned her liver, lung, intestine and stomach and did not find any cancer metastasis.
Now here is where it gets confusing:
They performed the nuclear imaging on the bones after the surgery in order to inspect if there was any legions.
They found that there was a a stain on the skull.
After that, they performed a CT scan and found that there was thickening of the inner layer of the skull on top of the DURA layer (right side of the parietal bone Aprox 2.5 cm above the ear).... the dimentions: 3.5 * 1.9 * 0.9

The doctors first said that the dont expect this tumor to be a metastasis.
Lately the doctor called us and said that they think it might be a meningioma en plaque and they scheduled her for an MRI to know with certainty.
Now since I am really worried, I started researching to see what can be the difference between a metastasis of Breast cancer and a meningioma on the CT scan.
Does the fact that it resembles a meningiome on the CTscan cancel the possibility of it being a breast metastasis?
How can a left breast cancer that hadn't spread to the lymph nodes and not as aggressive as the HER2 positive breast cancer pass to the right side of the skull and still have the time to create a tumor with a big dimension?
Doctors told us that it is unseen for someone to form 2 cancers in two different organs in the same time. Than how is this possible?
If it is a metastasis and it shows a single tumor than is it possible to treat it and does she have a chance of becoming cancer free again?
Could this be a cyst or the CT scan would show it?
What you general opinion about this case and what could this stain be?

Thank you and I hope I did not ask too many question but google's resources are limited and these are the ones that google couldn't answer!
Thanks again
Gus Karam

[guskaram]

I read my article again and I found many spelling mistakes.... I wrote it while I was in a hurry. So if u need any clarifications please feel free to ask.
Thank you

[guskaram]

I would also like to add that the results from the mri came in today and the doctors said that they don't know yet so it needs a biopsy. Does this cancel the possibility of a benign meningioma?
What could it be?
Thanks!!!