She’d blast music from a portable speaker, let the kids run dripping through my house, and help herself to whatever was in our refrigerator.

“It’s family,” David would say with a shrug whenever I voiced my concerns. “She’s my sister, Alisa. The kids love it, and it makes Mom happy. Don’t be so uptight.”

The breaking point came this past July. David and I had been planning a camping trip to Yellowstone for months. The only thing we needed was a larger tent. I remembered that Cassidy had bought a beautiful, four-person tent the previous summer, used it once for a weekend trip documented exhaustively on Facebook, and then stored it away. I figured she’d be happy to lend it to us, a small return for four years of unlimited pool access.