I was going to suggest the same thing as Glacier... get her checked! My friend's dog was diagnosed with Pancreatitis. Apparently, a dog will either have it from birth (which sounds like Chloe probably has) or will get it following an intestinal infection. You'll have to give her enzymes, but it's highly treatable! It's weird, but I have met several dogs with Pancreatitis in the past few months. I used to know nothing about it, and thought it was super rare... but my friend's dog was just diagnosed, a dog at the park had it, and a dog in rescue was diagnosed with it, and they are all healthy with treatment.

Since the episodes are sporadic, it doesn't sound like Chloe has a severe case... but I've read that a dog with Pancreatitis will slowly starve to death, so it's SUPER important to get her checked out! Unless they're absolutely positively necessary, I would skip the vaccinations, until Chloe is better. Good luck, and keep us updated!