“When Your Child Strays from God” by Sam J. Miller, published in July 2015 issue of Clarkesworld.
Description, from Best SF: "The story features a most unlikeable protagonist, unless you're a member of an Evangelical Church like Bethesda Wilde is, and share the seething anger and hatred that is bubbling under her skin. Her husband is pastor of the Grace Abounding Evangelical Church, and she is a joint pillar of the community. Sadly, her once beautiful (and pliant) son) has gone through puberty and the awkward teenage years, and has progressed from being a little naughty at times, to having started taking the newfangled Spiderweb drugs and left home – to live with ‘That Whore Susan’. Beth is not going to take this lying down, and she heads off to Susan’s house, having taken the Spiderweb drug herself – and this new-fangled drug has the unique property of making users of the same batch share their hallucinations. And so she is off on a short car drive with some strange hallucinogenic companions. The story cleverly reveals more about Beth and her background as it progresses."