As a parent, I feel like clothing sensory stuff isn't worth the misery of challenging. Try to get school to compromise. Cut out labels. Use seamless socks. Allow joggers instead of tailored trousers, but make them the right colour and closest possible shape, etc.
WRT behaviour...assuming she does turn out to be autistic.
Kids do well if they can. She will know that it's not ok to swear at Mum or kick out at her brother or whatever the behaviour is. It's not that she doesn't know what is expected of her. It's that, in the moment, something is stopping her from expressing her disagreement/unhappiness/ frustration in an appropriate way. Systems that use rewards and punishment assume that the missing factor is motivation. This is why I almost never use rewards and punishments, or suggest them.
What all challenging behaviour boils down to is that the child's skillset is lagging developmentally, and/or there is an expectation on them that they cannot meet. This expectation can be self-imposed or imposed by an adult. The context is also vital, for example personal resources are more limited when one is tired or has had a load of crap to put up with already that day (and that is, to be honest, the daily experience of many autistic kids in education).
So, reduce the expectations where you can, empathize with the person, acknowledge that things feel hard for her just now, and when things are calm try to come up with a plan to do things differently.
The plan A, B, C model from The Explosive Child by Ross Greene is absolutely brilliant. His website is called Lives in the Balance and includes videos outlining the key ideas above. I am a big Ross Greene fangirl :D