She's not much of a tweeter. As far as we can tell, she sent her first tweet today.
Most of Twitter's board members are fairly quiet on Twitter, as this chart from Quartz shows.
While it's easy to think of this as a bad thing, it's probably fine. A normal Twitter user doesn't jam out a lot of tweets. They sit back and read what other people are creating. If Twitter's board members are reading Twitter like the rest of us, that's not a bad thing.
Business Insider