I haven't done an Arkansas return lately but with other states, the software figures the best way to file, which is often MFS on a combined return.  It won't let you use the method that costs your client more in taxes, unless you override.  There might be a box to check on the state information sheet that will allow you to do that.  But make sure there's not a marriage penalty for MFJ.  When both have incomes, there might be.