Help with mesh? {SOLVED}

Most likely it happens due to different amount of bones in original mesh. I see that your mesh has b__ROOT_bind__ joint which is not suppose to be in skirt mesh. Extra or unnecessary bones will cause such glitches as on your screenshot. Don't use CC meshes as reference mesh, instead use EA's item. In this case I suggest deleting all bones in your mesh and redo weight transfer from EA's mesh. Transfer weights only to the skirt part, don't touch the legs.