There's a few things I realized that finally made me understand how to truly continue with my lifestyle as a vegetarian (no meat) and overcome the peer pressure:
-if you are under 18, chances are family will try and discredit you due to your lack of "life experience" but understand change doesn't happen over night.
Find support elsewhere
-You DO NOT need to prove to anyone why being vegetarian or vegan is valid. It's your life, your body.
-Confronting those who come across as peer pressuring.
Such as saying "I don't wish to talk about this anymore." "I don't appreciate you pressuring me so (please) stop." "If you actually care about me you'd let me live my life." "I don't barade your life choices so I'd appreciate it if you wouldn't barade mine." "I'd appreciate it if you'd stop putting me down." Sometimes people don't realize what peer pressure looks like so confronting them can open their eyes. Nobody wants to see themselves as the "bad guy" (peer pressuring) so think of this as a way of letting them know they went too far and it hurt your feelings. If they truly care about you they'll stop, otherwise it's time to start reconsidering "do they respect me? My life choices?"
-Understanding walking away from them isn't giving up, sometimes, it's stopping to put up with some people's bull crap.
-If family or friends really love you or care about you, they'd love & care about you regardless, not put you down about your life choices. They'd bring you up.
This was hard for me as low self esteem me still wanted to believe they did care but in the end it more about them than my actual health as why it was peer pressure and not support.
-Being open minded comes in short quantity sometimes, so not everyone welcomes difference in groups. So be the example, be open minded to their opinions, arguments, don't "prove" them wrong like they may do to you and show them you respect them because in turn if they don't respect you and continue to put you down for it, and you've confronted their behavior (how they have hurt your feelings and you don't appreciate it), continue to make jokes you've said make you feel uncomfortable, then it's time to move on to someone who does
Honestly, I've had a similar experience being vegetatian for about 6 years now and aspiring to be vegan once college is over. Before being official, I started under my parents roof, so claiming to be a vegetarian was almost like stating "cook my food without meat in it!" in the eyes of my parents which was more work for them (their perspective).
I ended up eating meat at first every once a week because of the peer pressure I recieved from all my family members who were of southern culture (big steaks, all the potatoes, gravvy, etc.) I hope this helps anyone having a hard time with choosing a less common lifestyle choice.