It is expensive and time consuming to become someone's guardian. There are better alternatives for your situation. Social Security has a Representative Payee Program. This is a financial management program
for SS beneficiaries who are incapable of managing their SS payments. Family members or friends are usually appointed as representatives. With this program, you open up a checking or savings account to receive your grandmother's check. The check can be direct deposited every month. You are responsible for spending the funds on behalf of your grandmother. Once a year, you need to report to SS how the money was spent. This can be done online. Contact your local Social Security office for assistance.
The VA has a similar program called the VA Fiduciary Program. The purpose is the same, to oversee the financial management of VA benefit payments. You set up a separate account and your grandmother's monthly VA benefit payments are direct deposited into this account. You can spend these funds on your grandmother's behalf. You can make a request for this service by sending your grandmother's name and file number along with your contact information to the VA Regional Office nearest you. Include the reason for your request. To find out the address of the VA Regional Office, I suggest you search online. The alternative is to call (800) 827-1000, but this can be very frustrating.