Love the collage, very pretty. And I hope your yarn smells better! If that doesn't work, try putting the yarn in a plastic bag with a dryer sheet for a few days. Its seems to work for me. :)
Removing essential oil is like removing any other greasy thing from a fabric/yarn. Washing didn't work because the detergent you use doesn't dissolve oils, try with soaking in warm water with detergent for dish washing (that's made to remove oil from dishes).