I agree that you're NOT nuts. But maybe these other people just don't hold very high expectations for your stepdaughter. I have seen countless people that think kids are "just supposed to be kids" - messy, impolite and ill-mannered. They treat their kids like adorable little idiots.
I will say, similar to some of the other postings, I am more careful to have "nice" clothes, for church, dinners out and other family events. My girls are taught to take EXTRA good care of these clothes...in the hamper or on the hanger, no exceptions. The same goes for their "good" shoes...they do not go outside for playtime. They are to be kept clean to go with out special clothes.
I do have "play clothes". Most of our clothes are what I would call "everyday" clothes. The ones with stains, small tears, etc. have been taken out and put in a downstairs cabinet...these I mostly use for when my kids are going to get messy (mud, sand & water table, etc.) I will put these "play clothes" on them OR if they get what they are wearing dirty, I put them in these "play clothes" as their second set of clothes for the day. Usually these go on late in the day when the kids are still 1/2 dirty so they can continue playing while I'm making dinner. I can't see putting "clean, everyday" clothes on 1/2 dirty kids while they're still busy playing. With that said, everyone in our family has "gardening shoes" that we keep on hand in the garage for those days where we're planting or working outside and need gym shoes for slopping around in.
I think you're right on track. Maybe if you change what you say to your family, don't focus on the "play clothes" but instead focus on keeping some "fancy/special" clothes. That way it's just a few outfits and 1 pair of shoes that you're keeping sacred instead of focusing on keeping the majority of her clothes unstained???
I hope this helps!
Sara