@oneundecided You are right. Looks like OK mandates state tax for non-residents if the income is $1000 or more. SO I presume we need to file OK state tax for the scholarship amount like $2.1k housing aid and any excess amount from other portion of the scholarship. Also I assume the $625 / semester check we get for National Merit Scholarship is OK income. But good news, OK tax rate is so low. For $3.5k income it comes to around $30 or so. That is good.
Fortunately in our case, my D does not have to file CA state tax since you need to have income around $16.5 to file. So she needs to file Federal and OK Non-Resident State tax only.