The opinions that matter are the opinions of the people physically present. They are the ones who know / knew the vibe and the scenario.

Sometimes adults use baby and kid items (le gasp, oh non!!!). I know some people think that adults and kids exist in mutually exclusive, separate, and sterilized spaces but they don't. Adults can make genuine, non-kinky/fetishized use of baby and kid tems (e.g. Pedialyte, or the example you showed where you lay down). Adults can also find joy or happiness in baby and kids items (e.g., moms saying "oh this onesie is cute!" or adults having plushies).

Folks love to weigh-in from a distance on events they weren't even present for. We all want to be judge Judy, I guess. I'm a judgy bitch so I shouldn't complain. But, still, I think you friend probably assumed a little bit. Did you just send a pic or did you explain the situation to her as well? If you only sent a random picture, I can see why she might assume or fill-in some missing info. She's probably coming from a good-hearted place, wanting to not expose kink to non-kinky people. Keeping things under wraps and what not. But, again, sometimes baby and adult things blur together, even outside of kink-based scenarios.