You can fill out a regular OK Form 511.

In the Personal Info section, mark her as Deceased with her date of death (screen shot attached), and the information will carry to your OK return.  

To make sure, check to see if the box to the right of her social security number on page 1 of her 2018 Form 511 paper copy is checked before submission.

Yes, I know how to fill out the oklahoma return.  But is there an additional form I need to fill out to claim her refund for myself?  Anything similar to a 1310?

Sorry, I didn't understand the question.

Yes, you need to fill out an OK Form 507, Statement of Person Claiming an Income Tax Refund Due a Deceased Taxpayer.

Thank you.  I have to mail in her return.  Should I send form 507 with her Oklahoma return or send it separate?  

No, send it in separately, to the address that I've listed in a screen shot.