Today, she told me that she accidentally mixed up some cans, and sprayed all her irises with Roundup, not fungicide like she had thought. She discovered her mistake later, and hosed them down, but doesn't know if it took---time will tell.
I hate to say this, but this pattern is looking an awful lot like signs I've seen in people's parents who were starting to have age-related mental problems. She's only 59, but that doesn't necessarily limit it.