.

just think of the positives

Explain it to her, I´m sure she understands.
Its not like its the end of the world

Just tell her, is not a very big deal I think, but depends of your mother mentality.

She loves you, she will understand. All you need to do is speak and be your true self.

And also make sure to get plenty of protein from somewhere. Being vegetarian is only funny when you start to do it as an adult who is after the growth period, or when you really carefully select what to eat.

It will sound a bit shitty, I know, sorry in advance, but do you think that 14 is an age where you can decide something like that for yourself? :/ Maybe at least ask a doctor first? A dietologist? We're supposed to eat animals and animal products, you know. Just check the food pyramid. Again, I'm sorry about my comment, but that's what I believe and I'm a food technologist.

its no big deal i turned vegan look at me lel :p same guy eating different shit no bigge

Maybe you should ask in reddit or tumblr, or some more specialized forum.
Have you spoken to your doctor/nutritionist about what it entails?
If you prepare your own food it's fine, if not, you should consider what the extra work for her to cook a special second meal for you would be.
¯\_(ツ)_/¯

can i ask you why you wish to become vegetarian?

It doesn't look like a big deal... I suppose we need some context here. It could be quite a big deal if i.e. she is butcher or fisher by job or something like that...

On the scale of 1 to 10 of bombshells that a 14 year old could drop on a parent, wanting to be vegetarian isn't going to be on the upper end of the scale.

Does she currently prepare all your meals? If so, you could use it as an opportunity to start preparing meals together. It could be like a bonding experience. And you're going to want to be able to prepare your own food if you're serious about being vegetarian. You can't rely on being able to get good prepared meals out there.

Oh and as others have said, research your diet properly. You need to put a lot more of the right stuff in to ensure your body gets what it needs.

Why do you want to become vegetarion, may i ask?

Cheers for the decision mate.
I have been a vegetarian my whole life. No one in my family believes in killing animals for food when there are alternatives available.
Its hard to just tell you how to tell your mum, but if you wanna talk about it, add me on Steam.

What's the big issue here? My family wouldn't have a problem with that, I just had to make my own meals

<facepalm>

It would depend on what her views on the topic are (and how strong they are), but try just talking about it to her, chances are she'll understand. You don't have to be absolute about it. Try asking how she'd feel if you gave it a try. Ask her if she would be okay with you trying it for a week or two, or a month. If she is cooking for more people, running parallel diets can be tricky at first. Offer to help out.
Basically, ask nicely, listen to what she has to say and present your side of things. If acceptance seems difficult, compromise. This is your mom - she wants you happy. If she has concerns (about your health, feasibility of it etc.) do some research and try to dispel them. Show her that this a decision you have thought about and that you are willing to be invested in making it work, and stopping if necessary.
Don't present it as rejecting of things so far - it's just trying something new.
As in most potentially difficult conversations, do your homework on the topic, listen to the other side and work towards a solution.
It'll be fine. Like Malorn said, she'll most likely understand. She might try to dissuade you if she is opposed to the decision, but it's not an attack at you. She's just being mom.

I have been a vegetarian for a very long time now and since then my parents have been mocking me for it. But they do respect my decision and they never force me to eat something I don't want to eat. My brother mocks me heavily for it but whenever I go to visit him he always takes me to restaurants that have lots of vegan/vegetarian options (even when he can't find something to eat for himself in those restaurants even though it isn't something I particularly want from him).

You just have to talk to your mother. She is your mother and she loves you. You just have to come clean and explain your mother why you want to become a vegetarian. I am hopeful that your mother will at least respect it.

there's nothing difficult about this, just tell her :D not like she's going to force you to swallow meat.
difficult would be if you were homosexual and would try to tell her.

It's not like you're going to tell her that you're a murderer, she'll most likely understand and accept that you want to stop eating meat if you explain it to her. No need to be afraid, the worst that can happen is that you'll have to make your own food, which isn't really anything bad either, it's just good to know.

Just tell her: “If slaughterhouses had glass walls, the whole world would be vegetarian.” or “Veganism is not about giving anything up or losing anything; it is about gaining the peace within yourself that comes from embracing nonviolence and refusing to participate in the exploitation of the vulnerable”.

From my own experience I can tell you that eating vegan (my case) is the best thing in the world. There is absolute NO argument against eating vegan, or becoming vegetarian. Why people get angry with or say it's dangerous is only because they don't want to hear the truth or they like it too much themselves (this is okay, because it's really hard to change things that you have been conditioned with as a child).

“I choose not to make a graveyard of my body for the rotting corpses of dead animals.”
― George Bernard Shaw

"Mom, i dont want to eat animals nor anything massively produced by them because i dont find it ethical"

but for some reason I find it quite difficult to

Try to think harder on this one, because like most here, I can't see a reason why this would be difficult. Once you can answer this question it will be easier for you to decide on the right tactic.

Try actually doing it for 1 month before telling her, are you hoping she supports/helps you if you tell her? Large lifestyle changes like this don't come easy

You are 14, in a year or so you might hardly even remember this phase