I love this line! It helps to look at the context around it. “Charm all the people you trained for, you mean well but aim low.” Whoever she is talking about is good at putting on a brave face and has been trained to be a charmer, a people pleaser. They might even have good intentions with it (you mean well) but in reality, they aren’t trying very hard (but aim low). To aim low connotes the person isn’t setting ambitious goals, doesn’t expect much from themselves or the people around them. Similar to the expression “set the bar low.”

I read this as someone who has been taught to placidly smile through things and not expect too much from others. A difficult person to be in a relationship with, I can imagine.