I am the quintessential over thinker!!! No less so with gardening, but you all have taught me that there isn't much you can't do over when you garden, so at least as far as gardening goes, I've gotten a lot better at the whole over thinking issue!
I had this very discussion with my sister this weekend who has had her garden re hard landscaped and had me over to plant up her beds. I’m very much a relax and go with the flow gardener, but I like a softer, informal garden, which is what she wanted, but she stressed and panicked and started planting her new plants like rows of veg on an allotment. Im hoping after a day with me, playing with the plants, she feels less stressed about gardening.
EJ, I had a neighbor who planted everything at just the right spacing, in nice straight rows, and kept the plants upright, pruned, and regimented. She told me our gardens looked "like a jungle." The second time she mentioned that, I told her jungles were filled with life, plants thrived, and the local wildlife knew their way around the "jungle." Your sister will come around--just give her time and her stress level will lower. Plants and cats do what they want, and she will learn that (at least about plants!).