I don't think "guilt" is the right word here either. She is expressing disappointment, but it's disappointment with what the person did, not with who the person is.

And while she's doing that, she's implicitly expressing the expectation that her students can do better. That's actually a far cry from the way lots of parents use guilt in traditional societies, where the implicit message is, "You did bad, again, just like I expected you to!" and the aim is to elicit effort through neurotic self-hatred.