What's wrong with my office manager sending my assistants off to other careers like kids leaving home.

In the recent past I hired an office manager, a full time assistant and a part time assistant all around the same time. I didn’t have any expectation that I would keep these people for ever, but I would have liked the opportunity to offer them an apprenticeship. But in the course of six months my office manager has convinced one of the assistants to change her major to nursing and go into that. The other assistant she is trying to send her into the same route. My manager explained to me that she thought these were better careers as even though they had more income potential with me, the medical field was more stable (true). Now I’m investing in people I know won’t be staying with me.

Now let me say that what she did for the assistants isn’t a bad thing and maybe that’s just the breaks for me. Other people have said the manager feels threatened. Well I hear all that but the question I would like answered, what’s bothering me about this and is there an action on the managers part to call her on. Is she allowed to not share my vision and work her own agenda?