It depends. Sometimes a story labeled as such might draw inspiration from real events but have fictional elements added. So, it might not be a purely true account.
It isn't a true story. Usually, works like this are crafted to engage the readers' imagination and provide an interesting fictional narrative rather than representing real-life events.
It's not a true story. 'Wicked Little Letters' is most likely a piece of imaginative writing crafted to captivate the audience and take them on a fictional journey.