Once upon a time, my advisor met weekly with her undergraduate honors thesis students. The meetings were only half the time devoted to her graduate students, but they were consistent. She helped them choose their projects, decide what to do when problems arose, analyze data, and write.
Then she realized that she had graduate students who could do this for her. The transition started gradually and ended abruptly; suddenly, she met with the graduate students, and the graduate students met with the undergrads, and never did the faculty and undergraduates see each other.
One of my thesis students has been working with me since she was a senior in high school. She picked up one of my side projects - one I would like to do if only that dissertation didn't get in the way. "Our" faculty advisor helped me brainstorm the project, but has been uninvolved since then. She has not met individually with my thesis student. She has not emailed her. She has not responded to my student's emails, beyond instructions on how those emails should be done better. She did not attend my student's lab meeting presentation at the halfway point of data collection.
And now, suddenly, out of the blue, she emailed my student asking why she didn't do *this* instead, where "this" is a plan we had specifically decided against in that lab meeting, and my advisor had implicitly condoned. If the thesis time constraints were really that important.
Which means I sent a very careful but adamant email reminding the advisor that a decision had been made at lab meeting, that if she had any problems with that decision she should have said it then, and explaining exactly how tight the constraints were.
I did not say that she had no business interfering in my mentoring relationship with my student, or butting into a project she has had nothing to do with for almost a year. But I really, really wanted to.