It may have been disrespectful, but sorry, it was funny.
I read a little about the incident before I posted, and the post-anthem act was suggested by one of the PR guys with the Padres. I’m not terribly sensitive to disrespectful behavior, but I didn’t find it funny. I think part of it was the context; she had just butchered the anthem to the point the crowd was booing her, so it looked like classless lashing out, even if it was actually pre-planned.