"They both flirt with other people, but Ramona was shocked to learn that her husband was actually seeing someone," the friend says. "Neither Ramona nor their friends thought anything would go beyond a flirty stage."
The reality star, 57, filed for divorce this week from her husband of 22 years, and while Ramona loves Mario, the friend believes Ramona and their daughter Avery will be fine no matter what happens.
"Of course it hurts, but Ramona is like dynamite and Avery is also strong," the friend tells PEOPLE. "Ramona has her own business, the TV show and lots of hobbies like skiing and tennis."
"She will survive," adds the friend, who believes her pal will come out of this stronger and happier – especially after she gets her revenge on her 60-year-old husband.
"Ramona will stick it to Mario. She is bubbly and fun and will find herself plenty of younger guys!"
Season 6 of The Real Housewives of New York City premieres March 11 on Bravo.