Sorry to hear. Yes, typically someone needs to file for her, if she received tax forms. When you start TurboTax in the personal section, it will ask if you're filing this return for someone who passed away. Her sister would indicate that in the software. If she didn't earn that much money in January she may not need to file for 2017.
If she has a refund, you usually want to file to get the refund. You can update TurboTax for free and you don't have to pay unless you want to file. Also, the IRS has a interview tool, to find out if filing a return is required, which you can check out HERE.