Good question,
I've never read that anyone had scar tissue show on their standard MRI & not sure about the 3 d one either.

I do recall reading that some had surgery & the scar tissue was found by the dr during the operation and removed. But for some it did come back over time.

I think that some people just tend to produce more scar tissue than others.

How can she tell it is scar tissue, did she describe how it feels to her?
Do you think you ever had a injury to that c7 area?
car accident, sports, any falls?

I think scar tissue can stick to or impinge the nerves, as well as arteries/veins/muscles...