Deceased parent with no executor

Hello

 

Me and my siblings are debating if we need to file a 1040 tax return for our mother who passed in January of this year. My sister wants to file an extension for now. I believe we do not need to file anything. My mother did not own any assets, has no money in her bank account, and passed without a will or appointed representative.

 

She received annuity and social security last year. And a tax estimate shows she will owe about $1,200. 

Can anyone please shed some light on this? Does anything need to be done ? Thank you