The translation should be "Your coat is very big for her" -- "too big" is "demasiado grande":.
Literally, that is correct, but that is not a sentence you would normally hear in natural English. I actually prefer it when the program forces more natural translations. It gets you in the habit of realizing you aren't supposed to be translating word for word.
I guess the question then is, would this sentence ever actually be spoken in Spanish?
this is the first time that I hear "eja" and not eya for ella... are both correct?
In different parts of the Spanish-speaking world, the double L is pronounced with more of J sound; both are correct.