It's difficult to know for sure without knowing the size or type of object ingested, but it's definitely a concern for causing an obstruction in the stomach or intestines. If she ate it within the last three hours, then it's possible that it can be retrieved from the stomach if you take her to the vet. This may require anesthesia and special instrumentation though, so it would be expected to be somewhat costly - especially at an emergency clinic. This is the best option though.
The other option is waiting to see if it passes OK. Normal GI transit time is 3-5 days. During this time you would just be waiting to see if she has any signs of an obstruction. Signs of an obstructions are vomiting, not defecating, acting very painful/depressed and a decrease in appetite. If you notice these signs, then Olive would need to go to the vet immediately for emergency surgery.
I hope that helps and all is well with Olive.