You are not “over sensitive” - in fact you are under reacting to an undermining narcissistic bully. People like her need to to put people down just to stay afloat. This is an “emotional discharge” for her of her own toxic feelings - when she does this she feels relief from her own inadequacies and no doubt repressed anger about the shit marriage she is in. She Ian also showing Narc tendencies lying about stuff and briefing you about what to say to her relatives but at the same time inserts herself into the reflective glow of your achievements.
Every child requires and deserves to be championed, applauded, supported, cherished, guided, encouraged. That’s the fertile soil they need for healthy growth - they need protection from the bitter insidious frosts of criticisms and belittling.
These are not small things, minor nit picking - these are words and actions that create the core of who we are, how we see ourselves and we carry this through life and will determine our emotional stance, resilience, self esteem and maturity which will then determine our “success” in life - eg wide range of equal and radiant friendships and stable and emotionally nourishing intimate relationships. From that successful, fulfilling careers fall into place.
Your parents didn’t provide enough / any of the basic materials to grow emotionally strong and balanced - you are at a good point now to recognise that - and fill those gaps now. There are lots of resources online to look at personal growth.
You have taken a v significant step on this journey already. The next one is boundaries - each and every time calmly and assertively with consequences. Never get into the details - but have a generic response ready - even if you only feel
able to text it the next day:
Your negativity around x is hurtful and unpleasant. Don’t do that again.
But your real boundary needs to be emotional disconnection in your head ams physical distance.