two right arm mistakes

as you can see i have one layer that is a full image of my water based girl and i have a second layer that is her right arm the reason i copied that right arm and turned it into its own seperate layor was so i could easily edit the right arm without also editing the rest of her but as you can see unless i keep the right arm layor in the position its in you will see her second right arm how do i get rid of the first layors right arm so the only right arm you see is from the second layor thats named right arm or do i have to just erase the right arm in the layer with the full figured version so its not underneath the right arm layor in adobe after effects so this doesnt happen?
as you can see i sucessfully got the right arm layer with the full figured her layor but the full figured water based girls layors right arm is behind the right arm layor how do i prevent this?
