I understand that, we have often heard similar or the usual is “I don’t want it now, she has contaminated it!”
I’m interested to know something, does it work both ways with your daughter? What I mean is my eldest sees nothing wrong in helping herself to other people’s things if “no one was using it”, “I needed it”, “it’s not a big deal, it’s not deep etc” however like your child, she will have a major meltdown if anyone else borrowed or used something belonging to her for the same reason.
This strikes me as not only unreasonable but hypocritical. Just to be clear I’m not talking about prized possessions here or meaningful objects with sentimental value, that’s different. I’m talking about a pen, phone charger cable, a book she grew out of a few years ago and has no value to her etc, the expression ‘dog in a manger’ comes into play here. Of course much of this could be simply sibling rivalry I realise however her sister is happy to share, lend or trade.
I see what others are saying about why should children be made to share, but I think it is important for children with ASD to learn, or at least experience the concept of sharing at home in a safe environment where meltdowns can be handled safely. While a child may be able to control the environment of their room and possessions to some degree, once they are in a different environment things change.
At school, or work, a friends house etc things are different. Some people share and think nothing of it, and some people take what doesn’t belong to them and when confronted act offended and patronise with “I’m only borrowing it!” It’s not right but it does and will happen. A child with little or no experience of sharing is likely to be overwhelmed or incredulous to such common behaviour in the NT world. I do therefore think IMO it’s important to acclimatise and prepare children for sharing and other behaviours because while they don’t have to like it, they need to be able to cope with it when it happens, and like it or not it will happen!