Verb to be: ser / estar .. everything depends on the situation.. in this case, if you translate "she's very happy" you could use "ella está muy feliz" when you know that "ella está muy feliz" that she's living the moment and you know that she "está" very happy ... If you attribute to happy person you should use "Ella es feliz" from verb "ser"
Easy rhyme to remember...
How you FEEL and where you ARE, that is when you use ESTAR
Estar= estar, estoy, está, estás Ser = ser, soy, es, eres
You are brunette... not a feeling, not where you are, so you use Ser.
You are happy... that's a feeling, use estar.
You are American... but you might not be in America right now, use ser.
You are in America... thats where you are, so use estar.
.... also "ing" verbs use estar, like jumpING or cryING
Also, if you haven't looked up charts for verbs with pronouns yet, I highly recommend it, helped me a ton. Idk if the rhyme makes much sense without it.
Anyway buena suerte!
I have also had this problem in another form: If I use Lopez or any other word that has a counter part in English I run into problems. If I use an accent mark over the "o" the spell checker the spell checker marks it as an error, if I don't use the accent mark the program chides me for leaving it out. Very confusing. I have found that generally, if some English speaker uses accent marks for words that in other languages like Lopez (when writing) it is considered to be an affectation. If an English speaker says the word as accented they are often viewed as showing. off and are often ridiculed. So, it seems you can't win either way.
Be careful with this one. Estar is technically correct since it's not permanent but Spanish speakers tend to always use Ser with feliz. A quick google search will confirm that. I've also spent 14 months travelling around 7 different Spanish speaking countries (Spain, Chile, Argentina, Uruguay, Bolivia, Peru and Mexico) my girlfriend is from an 8th (Venezuela). It's the sane in all so not country specific like a lot of other inconsistencies in Spanish.