Never Been Better by Leanne Toshiko Simpson

A hilariously offbeat and tender comedy about one bipolar woman's messy search for love at a seaside wedding where no one can stay afloat.
Is she falling in love, or falling apart?
Dee, Misa, and Matt were the "three musketeers" of the psych ward. A year after discharge, Dee is eager to convince everyone that she's finally turning things around. But Matt and Misa are tying the knot in Turks and Caicos, surrounded by guests who have no idea where they met, and the secrecy isn't sitting well with Dee, who has been hopelessly in love with Matt since before she got kicked out of the hospital.
So, when Dee arrives at the swanky resort with her high-voltage sister, Tilley, it's now or never to confess how she feels. But disrupting her best friends' nuptials would jeopardize the entire support system that holds the trio together. When it comes to happily ever afters, how is a girl supposed to choose between love and recovery?