I'd prob buy a white shirt in the style of the real shirt then using fabric spray do a similar design to hers with the colors merging. Then paint the top design on w fabric paint.
Love that mv by them
Adelheid (KHR!)- 85% done
Fem!Austrian War Succesion France (Hetalia/Nyotalia)- 10% done
Fem!Izaya (Drrr!)- 90% done
Magent!Teto (Vocaloid)- 95% done