I’m 25m dating 46f for 2 years. I get where you’re coming from, maybe more than most.
The number one thing is time. People need to see a relationship that defies normality, to last longer than normal.
Bear in mind, it’s equally if not more difficult for her as the stigma will be directed more towards her, I hope you family haven’t scared her off.
In time, people will understand. I still haven’t introduced my parents and my girlfriend.
Perhaps you made a mistake connecting the two parts of your life whilst still in a relatively new relationship.
Love conquers all brother and if she’s worth it, you’ll stay together.
P.S. I would have slapped my little brother off his chair if he’d said that to my girlfriend.