When he was small my son used to struggle with 'bumpy' shoes, and 'scratchy labels' and the worry that his shoes would fall off unless done up tight enough to cut off the blood supply to his feet! He used to have meltdowns over these things, but it was clearly genuine distress over the physical sensation of these things, rather than a tantrum. I used to find it bewildering and frustrating when it made parts of life so difficult, but then I came across the website below which talked about some people having overactive nervous systems that could cause sensory issues (not the same as Sensory Processing Disorder) AND emotional issues, such as anxiousness and 'timidity'. The website described the character traits as 'Highly Sensitive' - a name that I don't like, personally - but it really did describe my son to a tee.
What you write about your mindee puts me in mind of it too; She has gone to considerable lengths to avoid these uncomfortable sensations over a sustained period (thinking of how she's managed her difficulties with her cap and apron), and the fact that she really 'feels' her emotions intensely seems similar too.
Once I was able to understand my son's behaviour as coming from a genuine difficulty for him, I found it easier to be calmer about it all and worked to help him understand what was happening: "Your skin is really noticing the feeling of the sock at the moment, but it'll get used to it in a couple of minutes". I used to be understanding of his feelings, but let him know that whatever it was (ie wearing school shoes) did need to happen and encourage him to find a way to manage it - for example, with the socks he used to rub his feet really fast to over-ride the sensation of the sock on his skin. Or he used to run up and down the hall to take his mind off it. When possible we would find ways to work round it and find clothing/ shoes options that were comfy for him (like you did with the comfy painting t-shirt for your mindee).
Now that he's older he is has got used to the sensations and learned to cope with them/ notice them less (although it takes him ages to make his bed, because it all has to be 'just so' :rolleyes:)
I hope things get easier for you and your mindee x
The Highly Sensitive Child