is this wage theft?

I work in the cafe and all of us baristas are super fed up with our cafe manager, she talks shit behind our backs and is really annoying. I know this seems juvenile, but its been going on for months now and literally every single barista dislikes this boss, so its a pretty toxic work environment. We've brought it up to our store manager but she won't confront the situation at all, it seems like she doesn't care. It makes sense that she doesn't care because it's not a legal issue, but I still wish she would tell our cafe manager to stop being mean. I'm just upset and want to do something about it, hence the motivation for this question.

During the holidays we obviously had a lot of new hires and their training shifts were very disorganized. Our manager had several shifts scheduled where baristas that had only worked here for a month or two were training new hires by themselves. Is training a part of barista responsibilities, or is it only leads/seniors that are allowed to train? Does this qualify as wage theft since they are doing the work of someone with a higher wage than them? This feels pretty flimsy and i'm sure won't lead to any legal conflicts but is this something I can bring up with my store manager as a way to let her know I am serious about what's going on in the cafe?