Take away all food, give only water. If still not a little back to normal contact your vet ASAP. They may have to do more than you can do at the present moment. If she starts to vomit look for the collar. If no collar comes up, then the vet may have to go in there and get it out. Flea/Tick collars are very poisonous to dogs/cats if ingested. Your best bet to make sure it doesn't happen again is to use Frontline. It's more effective and less likely that the dog will ingest it. If there is an emergency vet in your area or close to you contact them ASAP if your vet isn't open. It's expensive, but worth it cause they can save the life of your companion in the moment.
I hope she gets better soon and doesn't have to go in for surgery to fix the issue.
Our prayers are with you.
Annie The Pet Nanny