Two things.
She probably doesn't exercise/do any outdoor activity. And, she probably doesn't know anyone over the age of 50 that does.
Cycling is not bad for you. Sure, you might get some treatable gyn issues from riding, but for a physician to admonish you like this is extremely unprofessional. It is NOT inevitable that older women shrivel up, get fat, and need to be inactive. I had only been going to my gyn for about a year when I developed a lesion because I needed a change in saddle. At that point, she was not a cyclist, but when I told her what it was from, she was like, OK, and I got a new saddle! She was in her early forties and about 150 pounds overweight. She is now closer to 50 and is a tri-athlete and marathon runner who lost all of that weight. I love going there, because she treats me like an athletic woman who just happens to be almost 60. One of my friends stopped going to her, because she pushes a healthy lifestyle. She is the one who suggested I get an E-string t treat thin vaginal membranes/dryness that was impacting my riding as well as sexual stuff. Never, never, never has she suggested I take HRT.
There are much stricter rules about physicians accepting gifts from drug reps today. That doesn't mean that some doctors don't have their "favorite" drugs and push them because they don't take the time to learn about new things/research.
You are the consumer; choosing a doctor is just like buying any other service. Research, get recommendations from others who are athletic, and most of all, don't let this stop you from getting regular check ups. You just need to find the right person.