Why does my mom tell me to be confident, but then shoot me down the moment I am?

My mom used to buy me books about how to be more confident, but at the same time she’d shoot me down any time I actually showed confidence. For example one time I was showing my parents around my college lab rooms, and I guess I seemed proud, and my mom said super sarcastically ‘sometimes (my name) gets all confident and I don’t even know why’ and it made me feel so ashamed that I had the audacity to be proud of my school. Also, now I’m a new mom and have a new house and she was visiting and I was proud to tell her about our schedule/activities and she completely shot me down saying she doesn’t get why I’m so lazy (for letting my son watch tv 30 minutes/week), why I don’t give her more home cooked food that I make (for my family) after ‘all the food she’s given me’ (whatever that means), and on and on. But in the same visit she told me I need to be more confident so my toddler sees a good example of a confident parent. Another example is when I was younger, she would always tell me to make and see friends more often but after a play date she would shit talk that friend and ask why I’m even friends with them and get me to break the friendship off.

I just noticed this pattern and I’m wondering what the point of her doing this to me was/is.