Is it permissible to take money from a sick sister without her knowledge to cover the costs of her transportation for medical treatment, knowing that she receives assistance from social security?

It is not permissible to take money from one's sister without her knowledge and permission, and shyness is not considered an excuse for this. It is possible to ask her for an allowance in return. Scholars have unanimously agreed that it is not permissible to take the money of a Muslim or a Dhimmi without their permission.