I dabbled a bit when I was in my 20s, but I am not a LARPer. This answer is mainly based on observation of my wife's years in the hobby.
My wife is a LARPer, for about 10 years now. In real life she is often shy and introverted, and even among good friends she remains quiet. I have to be careful in social situations because I tend to be very talkative and I'll edge her out of conversation if I get carried away.
But when she LARPS... she's a different person. I have watched her, live and sometimes on video people shoot at the events. You would not recognize the shy woman. She becomes the barbarian dwarf, shouting insults and challenges at her enemies; or the silent assassin who the entire community all fear for her stealth and her willingness to kill anyone for any reason, especially if money is involved; or the crazy half-fae, traipsing through the village dancing around fights while she shouts cheery nonsense; or the bitter ritualist... or whichever character she's portraying that weekend.
LARPing is her avenue for expression and escape. She makes the costumes, and adopts the persona. It's also helped her with her shyness in real life, as she's become more confident in her interactions.
Regarding your age/gender, most LARPs I've seen - and the fantasy one my wife attends definitely fits this mold - seem to have a more even mix of genders than tabletop, and quite a range of ages. My wife is nearly fifty, and she gives rides to young men and women in their teens and twenties frequently. In fact, a few years ago, she somehow convinced a couple of our daughter's friends from high school to try it, including my daughter's boyfriend, and now they all go regularly.
Regarding your friends... I'm not the best person to give an opinion. I've always been open about my hobby. I get books delivered at work and I tell anyone who listens what I do for fun. Even my shy wife is open about it. Sure, some people think its silly, or nerdy - but you can't live your life worried about what other people will think.
Go out and have fun.