That Summer Feeling by Bridget Morrissey

When a divorced woman attends a sleepaway camp for adults, she reconnects with a man from her past—only to fall head over heels for his sister instead.
Garland Moore used to believe in magic, the power of optimism, and signs from the universe. Then her husband surprised her with divorce papers over Valentine's Day dinner. Now Garland isn’t sure what to believe anymore, except that she’s clearly never meant to love again. When new friends invite her to spend a week at their reopened sleepaway camp, she and her sister decide it’s an opportunity to enjoy the kind of summer getaway they never had as kids.
If Garland still believed in signs, this would sure seem like one. Summer camp is a chance to let go of her past and start fresh.