Signs of You — Emily France

Ever since Riley Strout lost her mother two years ago, her survival has depended on her other family: the quirky kids she met in a grief support group at school. Jay, Kate, and Noah are the only people who understand her pain; each lost a loved one.
 
When Riley sees her dead mother shopping in a grocery store, she fears post-traumatic stress -- until Jay and Kate report similar visions. Noah, having seen nothing, withdraws. Soon he disappears, and Riley fears the worst. But the frantic search for him unexpectedly draws Riley and the other two into a mystery surrounding a centuries-old relic and the clues it might offer about the afterlife. By reaching for the ones who are gone, Riley uncovers hidden truths about those she hasn't yet lost.