Any suggestions on how to handle this?
I plan to say - you have taken some cash so you can feel secure about what you have - I understand that. But I cannot allow you to take all of our money and lock it away. Therefore I will continue to pay all of our family expenses out of my account but I cannot let you take any more of our family's money.
Wow! That's tough... .and scary. Talking to a lawyer sounds like the best thing to do. Can you open a new account for the family expesnses so that she cannot access that $ too?
I would make some minor tweaks to the wording. By you saying "I can't let you... ." I think she may see this as you trying to control her and this could cause her to escalate, making the whole situation a power struggle.
Can you focus your wording more towards validation + how the account being empty will harm the family + solution (you'll continue to pay family expenses) + asking for her cooperation by not taking out more money. Don't forget to use
DEARMAN . Will you try to reword it here and we can help you flesh it out more?