Answer:
Ella está contenta.
Step-by-step explanation:
Ella está contenta. This means: She's happy. In Spanish the verb "ser" y "estar" are different, even though in English they can both be translated as the verb to be. "Ser" is used to describe the characteristics of a thing or a person. "Estar" can be used to talk about a temporary state. It is grammatically incorrect to say "Ella es contenta", because the adjective contenta is implied for a moment and is not used as a constant characteristic of a person. It can be tricky for English speaking people to get the difference between both verbs. Happy, on the other hand, can be used both with ser and estar:
Ella es feliz (meaning she's a happy spirited person)
Ella está feliz (meaning she's happy now, she's in a happy moment right now).