I've been working for my current company for more than 2 years. I am one of the youngest employees (27yo) and I have had 0 problems because of that. I have always been considered "the kid" but in a very respectful fashion, like "you are very very good for your age" both personally and professionally.
A few months ago I moved to a different office with a different manager. Everything is great excluded said manager. I don't get along with her very well and sometimes I find it really hard to get my job done with her.
In the very last period I have been getting to know her a little bit better and when discussing personal things (for instance during lunch) in a group she is frequently very dismissing of my opinion by saying things like "you are too young to know" or "please shut up, adults are talking" maybe with a smile. She has been already "scolded" by other colleagues for this arrogant attitude but this seems to have very little effect on her behavior.
Now I don't want to become her best friend, so I try to spend with her as little of my free time as possible to avoid any kind of problem but this dynamic seems to be more and more present also during our professional time together.
Things at the moment are not too bad so I'm not thinking about leaving my job or even complaining to HR but I am getting tired of the situation and I would like to prevent the situation from deteriorating further.
The question: What suggestions can you give me to prevent the situation from deteriorating any further?