Girl About Time (Ruby Red #1) by Kerstin Gier
Every family has secrets, but what happens when you are the family secret? Gwyneth is shocked to discover she's inherited the family time-travelling gene. One minute she's shopping, the next she's trapped between centuries. But she's not the only time traveller. Soon she's caught up in a dangerous mystery with a gorgeous boy - and a secret society determined to change the past.