If you really want the most accurate answer call to find out what kind of stress test she was given.
I suspect a nuclear stress test, dont let the name scare you, its very/most common now and the correct way to do a stress test. Built360 in his post was spot on, also for more information just google it.
A stress test can be done without a treadmill IF the person is not capable of walking on one, the stress on the heart is then induced through an injection meant to stress the heart and mimic the treadmill stress test.
Its important to know a stress test is not reliable to show blockages of roughly less then 60 or 70 percent. So you can pass one with flying colors but still have a blockage or blockages of 60% or more.
Do to family history I have had a few nuclear stress tests, I did well even on the last one which was just recently in early 2021. But with my family history and some symptoms I was having, we then went onto the next test, which is the gold standard, bar none, to check the condition of your arteries and for any blockages and possible future trouble. That test which is the
gold standard is an coronary angiogram.
https://www.mayoclinic.org/tests-procedures/coronary-angiogram/about/pac-20384904
It is invasive and with any invasive procedure there is a chance of a complication. Anyway, because again of family history I jumped on it when they suggested it. Actually I was thrilled. I now know EXACTLY what I am dealing with and made my life adjustments which I was doing anyway to the most healthy diet I know as well as two gym classes a week of intense exercise as I have minimal plaque spots "all over" Doctor feels the way I am going with my diet -Fish, chicken, fruit, veggies I may never need intervention.
Its actually pretty cool if your into electronics and stuff as your awake though groggy for the procedure so you may or may not remember all of it but I remember watching multiple monitors and the technology with actual images of my arteries on the screens wrapped around my heart I believe. It was kind of eerie like a dream state ... The doctor then did speak to me as he was finishing but then when done went out and spoke to my wife because he said I most likely will not remember what he said, he was right, I didnt *LOL*
Since it is more expensive, insurance may not pay/approve unless you get a failing grade on the stress test or unless you complain to your doctors something still isnt right. You may need to be persistent with your doctor to get approval (or have proactive doctor) and I am only saying this so your mom doesnt ignore any issues because she did well on the stress test.
Anyway, you can call the doctor and only way to know for sure is ask if it was a nuclear stress test, I suspect it was and why the injection. You can then do a search on the type test she had.
Ps. I am NOT in the medical field, do not have any medical education, any part of my post is what I believe to be true and that of family who have had heart issues. Always talk to the doctor and with that said, if your mom still complains she should never keep that from her doctor just because one test came back good.