Welcome to JustAnswer.
If your little one is having an upset stomach from the butter this morning then there is a good chance this is a gastritis scenario. It has a chance to settle down on its own. The gold standard for treatment of vomiting in a dog is fasting. Generally vomiting is acute (meaning it comes on quickly) and can be taken care of without much trouble.
If this were my dog, I'd fast her for 12 hours (providing she doesn't have any underlying diseases such as diabetes that require she eat every few hours). No treats, no food, nothing. You can offer a small amount of water after the 12 hours, but don't allow her to drink too much at one time (placing ice cubes in her bowl so that she can't gulp water will help).
After having access to the water for 1 hour, I'd offer a bland diet of boiled rice and boiled hamburger (3 parts rice to 1 part burger) in VERY small amounts (perhaps 1/4 c every hour or so) for the next 24 hours. Once you start feeding the rice mixture, monitor for recurring vomiting.
If the vomiting doesn't start again, you can begin slowly mix in his regular food over the next few days until you're back to just it. If the vomiting persists through the night, or if she becomes lethargic, begins to have diarrhea or shows other 'unusual' signs, you should have her seen by a vet, just to rule out any sort of illness such as pancreatitis, severe gastritis, foreign body or parasite infection.
I hope this helps and I hope she rests comfortably through the night!!