When We Were Friends by Samantha Tonge
a secret society, where they used their unique gifts to solve problems for whoever needed help. On the night of the prom, it all went horribly wrong and their friendship ended abruptly and for good.
Now 19 years later, Morgan has a teenage son, who keeps asking about his father. Morgan decides to get her friends back and ask them for help searching for her son's father. As adults, they meet again, but the pain of betrayal still feels fresh. They manage to put their differences aside to help Morgan, but it all blows up epically.
This was so good! I found myself totally immersed in the story and couldn't stop reading. They are all full of faults, but that doesn't stop you from rooting for them.