If she was merely a developer or other non-public-facing employee, there would be no reason for her to lose her job. But she was a developer evangelist -- someone who should know that everything she says and does reflects on the company -- and even if you agree with her actions you can't deny that the storm surrounding them would make it nearly impossible for her to effectively work in a job which involves meeting and working with developers.

By that standard, people who make sexist jokes should automatically get fired, because it makes it much more difficult to effectively work in a job which involves working with women and male allies.

If someone makes sexist jokes which offend their co-workers to the point that they're unable to work together, then yes, they should be fired.

Certainly if someone working in public relations posted sexist jokes to their twitter feed I'd expect them to be fired.