Yo entiendo esa frase en inglés de la siguiente manera: "Me encanta la carne pero hoy finjo que soy vegetariana" Sin embargo, creo que comprendo tu idea por lo que una mejor opción sería: "Me encanta la carne pero hoy intentaré ser vegetariana". (Maybe you should change the sentence in English to achieve the intention you initially wanted. Instead of 'pretending to be' (which gives an idea of 'faking' you could write 'try to be.' For instance, I'm a meat lover but I'll try to be veggie today.)

Yo Soy nuevo a en Italki

Hola, es mi primero mensaje aquí. No sé qué a escribir. No sé muchas palabras, pero intento encontrar descubrir más. Gracias por ayudarme.

(Did that make sense at all)

Your text made sense because it only had minor typos. Don't forget about the diacritical mark over the vocals! :) 

Each is used to point out an specific thing. Either is when you have to make a choice between a thing an another. I think that's the best way to tell them apart but it's just my opinion :) (For instance, the last example you wrote doesn't sound natural because even if they're only two words you have to say 'each'. In case you want to compare, the sentence would be something like: "You have to make a sentence choosing either this word or that one".)