Congrats on the win!!
And yes: there are *many* people out there who will have no qualms whatsoever over selling sick, diseased, or bug-ridden plants just to make the quick buck. "Leaf Spot?" lol!
That's why it's really important to only buy from reputable folks. I've been burned I don't know how many times, and the really bad part is, with some plants I bought when I was just starting out, I thought their "going downhill" was my fault, when instead, they were already sick when they got to me, and I just didn't know enough to recognize it.
At least you got to the bottom of what was going on. I hope she replaces it with a clean plant...