If by “being looked at” you mean the camera facing straight at the said actor instead of just having it on the screen, you can use the approach @eldany.uy has explained. However, if you mean the other option, you might consider checking if the actor is being rendered. There might still be additional things to consider while implementing this approach so I did a little research and found this post: Check if actor is visible to player - #2 by SupportiveEntity
Under this topic, you can inspect other posts to further enhance the reliability but I think the post I included here will be sufficient in your case 