Do I deduce that the OP and husband have separate accounts, but all of them are joint.
We do this, mainly because DH's work involved lots of overseas travel to 'interesting' countries before mobile phones and computers and it meant I could pay his credit card and deal with other financial affairs if necessary,when he was away.
We have never changed this. However, although all our accounts are joint. Neither of us would dream of looking at or accessing each others personal accounts. Each partner destroys the cash cards sent to them for the other persons private account.
I suspect Sally's DH has always managed their financial affairs and, as a rule, she has been happy to acquiesce in this, any successful marriage involves a lot of give and take, but I think, this time her DH has overstepped the mark, and as he is not used to being ueired or contradicted on financial matters, he may make a fuss. But in a situation like this, you either go under or you grit your teeth and accept that you are going to need to cause a row and you go ahead and do it. Sally knows, that she will have almost everyone on GN to giver encouragement and support if she does tell her DH very firmly that this money is hers, that it is staying in her account and she will decide how to spend it.