Had she had a previous Angiogram or stents installed?
I'm male, age 66, and experienced Spontaneous dissection of the Right Coronary artery. The dissection occurred between two previously installed stents. The operative report gave three possible causes; a split caused by the harmonics, or vibrations of the heart beat causing the artery to split, trauma caused by the catheter, or the Ankylosing Spondelitis disease I've had for many years, which is a risk factor for this event.
Has she been evaluated for any connective tissue disorders, such as Marfan's syndrome or Ehler Dahnlos or vascular issues such as Kawasaki's disease or FMD which rarely only affects the coronaries. Other issues such as trauma or catheter induced dissection are also possible.
If the patient has connective tissue phenotype, then it is reasonable to treat hypertension and atherosclerosis aggressively with beta blockers and statins, in order to prevent other such events.