My federal is rejected because I file my sister as a dependent she is disabled and I take care of her. Is it possible for her to file and I also file her as a dependent.

[Rachel_W]

Yes, it is possible for her to file a return even if you claim her as a Dependent.  She just needs to indicate on her Tax Return that she is a Dependent of Another.  

At this point, in order for you to claim your Sister as a Dependent on your return, her return will have to be Amended first.  You can click here for instructions on Amending your tax return: How to Change a Tax Return You Already Filed.

Once you begin the Amendment process, you will need to revisit the "My Info" section and click "Edit" next to her name.  As you walk through the TurboTax interview process, you need to answer "YES" to the question "Someone else can claim me as a Dependent" and "YES" to "and this person will claim me on their 2018 Tax Return".

Once her Amendment has been processed, you will be able to e-file your return.