Depends on the reasons why she was late and if they were legitimate or not.
It really depends on how "invariably" she was late. If she was late almost all the time, and by 45 minutes or more each time, then it's patently irresponsible. She should have set a different time for the meeting every week. Or she should have blocked out her schedule to make the time. On the other hand, if she was late maybe 25% of the time, that's a different story. The CEO of a huge corporation is going to be late to a lot of meetings. It's the nature of the job. There isn't enough time in the working day for all the people, situations, and projects she needs to handle.
Having worked every now and then with C-level executives at huge companies, some much bigger than Yahoo, I can tell you that they're often late to meetings. Staff meetings especially, because staff meetings are standing, and standing meetings usually lose in an ad-hoc triage battle against spur-of-the-moment meetings. Almost axiomatically, anyone or anything important enough to hijack a CEO's time is going to be important enough to win the priority battle against a standing staff meeting.
All of that said, "invariably" needs to be defined here. Especially given the circumstances, i.e., requiring all direct reports in various timezones to be there every Monday on Mayer's clock. If it was, indeed, "invariable" -- as in, she was always at least 45 minutes late -- then she should have found a new time for the meeting. That's completely unacceptable.
(Obviously, this is easier said than done. At that level, the politics of moving around direct-reporting lines is going to be a nightmare.)
But I do agree. The complexity of scheduling increases dramatically as the number of timezones N increases. You try the best you can to schedule a standing meeting that accommodates everyone. Someone's going to have to make a sacrifice in convenience. As the leader, you should try to find a time that makes a sacrifice on your end, provided it's not too ridiculous.
Still, I don't see that as "unacceptable" behaviour. It's something to be frowned upon for sure and it would be great if she could be punctual all the time, but being the CEO of an incredibly large and diverse organisation, she could be forgiven if she was late due to some other meeting or work-related issues.
Also, remember she's getting only about 4 hours of sleep everyday and practically lives at her workplace, so I doubt she's being late on purpose.
I am using conditional logic here because, like you, I have no idea what "invariably" really means here. Writers have a tendency to throw around words that sound good, without always considering the true extent of their meaning. As a sometime-writer, I suffer from this problem myself. "Invariably" is a tall claim, which is why I'd like to see the evidence for it before rushing to conclusive judgment.
Sleep deprivation is classed as torture. Even if you're a Type A personality, 4 hours is not enough to avoid issues with basic cognitive competence (at best) and general mental health (at worst).
See e.g.
http://www.nytimes.com/2011/04/17/magazine/mag-17Sleep-t.htm...
While it's true that not everyone requires the exact, same sleep schedule or regimen, there is no human on Earth who can successfully go years and years on 4 hours or less every night. You'll pay that debt eventually, with interest. Maybe not today, and maybe not tomorrow, and maybe 20 years from now. But you'll pay it back. Often in the form of a heart attack, a stroke, or brain damage.
Unless someone is on their way to the hospital, there really isn't a reason to leave someone hanging.