Here is some more info I found online, Firecow, on what are called intra-articular cervical facet joint injections:
Paducah, KY, Pain Management CenterPosterA more detailed article from
eMedicineAs a medical term, "facet" is usually pronounced with the accent on the 2nd syllable, to rhyme with "cassette."
From what I've read, the patient is usually sedated first, then they numb the skin with local anesthetic, then they insert 22 or 25 ga. needles (thinner than what's used when you get blood tests) under x-ray guidance. It's a commonly performed procedure, and serious complications are rare. Hospital stay is not required. With sedation there's should be little or no discomfort.
You are correct that Depo-Medrol is a cortisone-like steroid (methylprednisolone), commonly injected as an anti-inflammatory without serious side-effects. (Not related to the anabolic steroid issues of professional athletes).
Wish her luck. It's hard to get rid of a few jitters, but no need to be in a full panic!