Everybody that's following her twitter stream chose to follow her twitter stream. That makes a huge difference. And it's also trivially easy to unfollow her stream if what she says offends you.

Also, the context is very different. You may think of PyCon as a social gathering, but it is in fact work-related for a lot of people (including, presumably, Adria in her role as a developer evangelist). What's acceptable in an informal, personal setting (e.g. jokes made to people who explicitly chose to view her personal twitter stream) may not be acceptable in any kind of professional setting.