Yeah, you'll probably suck the first time you ride. Pretty much everyone sucks the first time they ride. Some of us suck longer, too...
There will be plenty of 14 year old girls who will ride better than you for some time. Starting at 50, and lacking any aptitude for riding, there are plenty of 14 year old girls who can ride rings around me. Some of those 14 year old girls were riding as little kids, too.
I rarely ride around others, but I can honestly say no one has ever laughed at me - not to my face, anyways. Every teen girl rider I've run into who found out I liked riding horses thought it was great. I've heard things like, "I wish my Dad would ride with me sometimes". I've never had any female of any age try to discourage me from riding horses.
Well, maybe one. When I was 25, I made an attempt at learning to ride. I only had 8 weeks before the military was going to send me to the Philippines. I took jumping lessons from a very pretty young woman. The lessons, IIRC, consisted of putting me on a variety of horses and jumping a variety of things, helmetless and with no actual instruction. Looking back, she may have been trying to eliminate my genes from the gene pool. I'm surprised I didn't kill myself. It didn't help that I spent more time looking at her than at the jumps...which may have been why she was trying to kill me!
If you work at it, you won't suck long. That is one of the great things about starting young. Your body won't handicap you with 5 decades of bad habits, tightness and old injuries.