It does sound like a computer glitch and she may not have even been aware of it. You know how you can be working with an account (here, or a similar site or email account) and there's so many features you can accidentally change things you're not aware of. It sounds like she may not have been aware that there had been any problems.

When something on the computer happens, I always, always, always blame the computer first and investigate and only think someone has deliberately done something to the communication to me, personally (I'm sure your online counselor has other clients), when they confirm it, personally. That's why therapy is done in person, so one can check out what's going on, right away, in person.