Thank you very much for the replies! I didn't measure the end play of that pulley, but I would say it is more than 1/8th and closer to 1/4.
The original belt could have gone due to age. The car had well over 100,000 miles when I changed that one 4-5 years ago. The next belt I put on was one of the two that peeled apart within a week's time.
One thing I recall when I installed the 2nd belt, I did not care for how the new belt rode on the tensioner pulley. The outside edge of the belt seemed to me to be too close to the face of the pulley. In other words, it seemed like it shifted away from the engine in comparison to the wear marks on the pulley. But everything looked inline and I watched it for a while. The belt seemed to run smoothly. So I made a mental note of it and let it go. When she told me it ripped, I thought, "Well, maybe that has something to do with it." I expected to see the issue on the outside of the belt. I was surprised to see it was the inner side that tore.
So that is suspect, but I am still not convinced it is the culprit..... but maybe...maybe that excessive play did cause the belt to ride like that, then pulled in and out under forces, causing it to eventually fail on an inward misalignment.
I have R&R'd many things on many cars, but never a PS pump. Any special tools needed?
Thanks again for the replies. I know it seems dumb that I let it go with that suspect tensioner alignment, but this car is pushing 200,000 miles and, if it wasn't going to be an issue, I wasn't going to mess with it.