Far From You by Tess Sharpe

That’s how long recovering addict Sophie’s been drug-free. Four months ago her best friend, Mina, died in what everyone believes was a drug deal gone wrong – a deal they think Sophie set up. Only Sophie knows the truth. She and Mina shared a secret, but there was no drug deal. Mina was deliberately murdered.

Forced into rehab for an addiction she’d already beaten, Sophie’s finally out and on the trail of the killer—but can she track them down before they come for her?