Screeching and refusing to sleep

We've had 2 episodes of vomiting within a few days of each other with my 8mo. Since then when we start the bedtime routine and she's starting to get tired she starts screaming and working herself up. If we bring her downstairs she's absolutely fine. The time for sleep is appropriate but because she's refusing it and getting worked up she's now having 5-6 hour wake windows at bedtime. Naps in the same environment during the day is absolutely fine. She refuses her normal sleep associations like milk, dummy, being held and even though one day she fell asleep to her hair being brushed the next 2 days she refused it. We're at our wits ends!!! Any help???