A Question !
For the translation of this sentence : "Ella esta mal." I typed : "She is bad." and it was wrong ! the correct one was : "She is ill." Why??!
This had been always a question for me: What is the difference between "Estar" and "Ser" ???
She is bad... means "Ella es mala" but is the sentence is "Ella esta mal" refers she does not feel good so the translation is "She is ill" .
The difference between Estar and Ser is.....
--- Estar is using to express how we feel or where we are. ---Example: Yo estoy triste ..... Ella no esta contenta ....
----Ser... refers how we are like person. ----Example: Yo soy una mujer comprensiva..... Ella no es muy amable
The difference between "estar" and "ser" has been explained in one of lessons in the Spanish course:
"Ser" refers to what something is, while estar refers more to what something does. For example, "estoy enfermo" would mean "I am being sick" or "I am currently sick." On the other hand "soy enfermo" translates to something closer to "I am a sick person" or "I am sickly." You can think of "ser" as being equivalent to "equals." Alternatively, you can think of "estar" as refering to a temporary condition, while "ser" frequently refers to a permanent condition. However there are some exceptions. For example, "ser" is used in expressions of time, such as "son las cuatro de la tarde" (it's 4 in the afternoon). Also, "estar" is used to indicate someone has died, so "he is dead" would be "está muerto."
Apart from that, I can also add that "estar" is used to determine the place where a person is right now. So, for instance, you say "el libro está en la cocina" instead of "el libro es en la cocina" - which means "the book is in the kitchen".
In the context of your first question, "estar" is used to say how someone feels while "ser" is used to say what somebody is like:
Estoy mal - I feel bad / I'm sick. Soy mal - I am bad (a bad person).
So, Estar and Ser both have to do with state of being... you always use "Estar" with location, how one is feeling, something temporary. Look at this site, it is very helpful for understanding the uses of these two verbs: http://www.studyspanish.com/lessons/serest3.htm
As an answer to your question, "Ella esta mal," that means that she is currently/temporarily ill. Instead of using "enferma" duolingo used "mal." You wrote "she is bad" which would translate to "Ella es mal" indicating that she is a bad person or she is wrong. It refers to something more permanent, like her personality.
Hope this helps!