Yeah if you want to do this with individual images, you'll have to do something like.
image eileen happy = At('eileen_happy', sprite_highlight('eileen'))
image eileen sad = At('eileen_sad', sprite_highlight('eileen'))
# Or, if you'd want an ATL example
image eileen happy:
'eileen_happy'
function SpriteFocus('eileen')
It's definitely more cumbersome but I don't have a lot of good ways of working around this. Hope this helps though.