It sounds like you want to do this so she passes her hairballs out the back end vs the front end, right? For that, you could try giving her a teaspoon of canned pumpkin several times a week (though it sounds like you feed dry food, so your baby would need to like pumpkin straight, and some cats do and some cats don't.) Or, as Laurie stated, try using a fish oil rather than olive oil.
Now as to how to get it in her...that's the mystery. My own cats all four refused their dry food when I added salmon oil to it. Period. So that was the end of that in our house
(cat's RULE here) I'm thinking if they wouldn't go for fish oil, they certainly wouldn't go for olive oil. BUT, if your real objective is the hairballs, then you can simply give her a little bit of butter or petroleum jelly, and that should help. If she won't eat it flat out, spread it on her paw and she'll lick it off. (just a dollop, not too much)