I know how that is. My family is very traditional in many ways and are definitely "old school" about a lot of things. Even now my mother cringes when I'm blowing off steam about something and really wants to hear that I haven't said the things I'm articulating to her to the person I might be upset with because truth be told, I do have a mouth on me (but I'm getting better at that).

As a bicultural kid I did have to eventually put my foot down and tell my parents that though I love and respect them, there are certain misunderstandings and differences of opinion that are naturally going to occur given the difference in generation and in culture and that if they weren't willing to address that with me then there were much less desirable options available.

In the end, it was our mutual desire to preserve the relationship and to find ways to learn from each other that ultimately helped us get to a place where we could begin to try to approach each other from positions of respect.

Growing up is shitty sometimes and for a million different reasons. I'd be willing to bet (and I am a gambling man) that it's not only decorum that's dictating your mother's behavior, but things that are challenging her fundamental beliefs. When we feel backed into a corner, people tend to act in predictably shitty ways. If you're finding that therapy isn't helping, perhaps you might consult a mediator or conflict specialist of some kind.