Barbenheimer — and she’s been having a wild few months.Barbara “Barbie” Oppenheimer has experienced an exciting summer amid the double-feature of Greta Gerwig’s “Barbie” and Christopher Nolan’s “Oppenheimer” that sparked a mashup obsession on the internet.The 68-year-old grandmother of five is owning her name, which has taken the world by storm.“The Barbenheimer craze has added some more fun to my already good life. It’s been great fun,” Oppenheimer told The Post.