mum makes fun of my dreams

I want to be a doctor and am working hard on my application for medicine this year. I often portion control my dad's snacks because he overeats without realising and has diabetes and I care about him. I overheard my mum telling him 'be careful X is coming, she thinks she's a doctor now so she'll take your snack away from you' in a weird laughing whisper. Today she was talking about how her brother didn't take his pressure meds and is unwell and told me, oh you should call him and tell him to take his meds and be careful' is an odd tone. I don't tell her much about my aspirations as she told all her friends my grades last year and I don't like sharing these things personally (I haven't even told my friends what I want to do!). I just hate how she undermines me. I tell my dad everything but maybe I should tell him to not tell my mum? help