You are a GA resident until you proactively change. Just going to  school in MS does make you a MS resident, even if you live off campus.  If you are still a dependent, on your parent's tax return, you are considered to be living at their resilience.

Typically, you must get a MS drivers license and car registration and register to vote.  Your intent not to return to GA is a factor, but not enough in itself. 

You should file a MS non-resident return and a GA resident return. GA will give you a credit or partial credit for what you paid MS

You can file as a Mississippi resident if you meet the Mississippi residency requirements and are not claimed as a dependent on

your parents tax return. If this is correct then you do not need to file a Georgia return since all of your income is from Mississippi

sources.

Here is Mississippi's definition of "resident":

An individual who maintains a home, apartment or other place of abode in Mississippi, or who exercises the rights of citizenship in Mississippi by meeting the requirements as a voter or who enjoys the benefits of homestead exemption, is a legal resident of the State of Mississippi and remains a resident although temporarily absent from the state for varying intervals of time. https://www.dor.ms.gov/Provider%20Forms/80100181.pdf 

@mccallgabrielle - Bottom line: you can probably just file a MS return and not bother with GA. This is because  you will graduate soon and do not intend to return to GA.  This assumes you are not still your parent's dependent for 2019.  Since, GA & MS tax rates are similar, you come out about the same either way, other than the cost and hassle of filing a 2nd state

However, a student is usually considered a resident of the state he matriculated from, until he proactively changes it.