If this helps, Heart Catheterization is a good thing, it is the GOLD STANDARD to have her arteries checked for blockages. There is no better method and a stress test pales in comparison. At least she and your family will have a clear idea what you are dealing with. The procedure itself is a piece of cake, she will be given a mild sedative and will be awake for the procedure, she will not feel a thing, its kind of neat actually but chances are she wont remember most of it.
If they find a blockage, they, in most cases can take care of it right there and then by inserting a stent or stents, sometimes without a stint by simple compression of the blockage.
Where we can have some hopes and prayers is if there is a blockage its not so severe that she would need to go back for bypass surgery which of course is far more risky. But as far as the procedure tomorrow she will be fine.
I was lucky enough to have one back at the start of 2021 after a stress test there was some question whether to proceed with the Catheterization and they left it up to me for the most part. I jumped on the chance to get it, its truly the only way to know the condition of your heart arteries and prevent or deal with any problems.
I was lucky enough to have minimal plaqueing and no further intervention needed but it gave me a BIG heads up to take my diet to the next level.
I am the only male in my family to (so far) have beat major heart disease and diabetes.
Anyway, this isnt about me, its about your mom, she will be fine through the procedure, the scary part is what they may find. Ill say a prayer that its something that can be dealt with right there and then, if so, your in great shape, future diet is important.
Good luck to her!