What is the best neighborhood in Seattle for a single, professional in her mid 30's?

I would say Ballard. The food is great, the nightlife has something for everyone, and the D-Line is an express route to Queen Ann and Downtown.

The crowd in Ballard is a bit older so a 30 something professional would fit right in. The pace is more laid back than Capitol Hill, but still very alive.

The neighborhood has plenty of options for renting and buying. I also think the parking and traffic situation is much less of an issue versus Capitol Hill, Belltown, and others.