Each Live Event is different, so you need to purchase her again if you'd like to use her for a new Live Event.
This is outlined in the description on the pack before making the purchase.
She's a busy girl and spends a lot of time collecting various resources for each event. This type of pack is a new thing we're trialling - in fact, Laura is more of an NPC (non-player character) than a pack, so she's a bit more temporary! She doesn't quite work like the clothing you put on your Sims day-to-day.
Note: The game team have also listened to your suggestions and made adjustments in this update to make Laura more effective - she now collects more resources and spends less time doing so.