The most important thing is to be there cheering. Bring all the signs and noise makers you want. Check the course out ahead of time and see where the best vantage points will be. You could drive the course with your daughter the day before the race. See if there is a way you can watch her at the beginning and then hop in the car a drive to another place. I think it is important to be there at the finish. After a race it is really nice to see a familiar face when you have just given it your all no matter what the distance is.
Kudos for being so supportive. I have a friend who ran her first marathon without anyone there at all (I didn't know about it). Her boyfriend went golfing rather than going to her race! Her parents couldn't be bothered either.
When I ran my first marathon, my brother flew all the way down to Texas with me from Michigan just to be there and support me. It made a huge difference.