It is only the first night alone, so give it some time :) My almost 3 year old was obsessed with her baby brother at first and constantly wanting to hold him, etc. But she has leveled off quite a bit. She still likes to help and be involved. It is important to let your oldest know that they are still important and it will make her feel great to be a big help to you. Trust me, I can get mine to get me diapers, wipes, bibs, etc. It is awesome when you have your hands full :)
This! Take advantage of the help. My DD will rock the carseat if DD#2 is crying and I am running around trying to gather up things before we get in the car. She brings me diapers, wipes, blankets. DD#2 already really likes her. When DD#1 talks, #2 starts moving her head around like she is looking for her. When #2 gets upset #1 can get in her face and talk and it calms her down.