First of all, you need to know your financial situation and ability, whether you have enough funds to lend, and you need to consider that your financial situation will not be greatly affected.
Secondly, you need to check your sister's situation and make sure what she said is true. You can ask the hospital about your illness, or ask other relatives or friends for as much information as possible.
Finally, if you decide to borrow money, I suggest you write the loan agreement clearly, stating the loan amount, repayment period, interest, repayment method and other terms, and both parties sign it for confirmation. At the same time, we can also consider discussing interest and repayment methods in advance and how to deal with possible risks.
It should be noted that borrowing involves many risks and legal issues. It is recommended that you carefully understand and consider before borrowing money to avoid accidents and disputes. If you need more specific and detailed advice, I suggest you consult a lawyer or relevant professional institutions.