"I am disappointed she is leaving, we were just starting to have a productive relationship with the Chamber."
or
"Beth brought a lot to the Chamber and the city. She was part of the branding committee we formed to market the city in a better way. We need to sustain that effort with her departure."
or
"It's rare that you get just the right person at the right time - with her departure, we will have to rely on the same kind of luck that brought her here."