Practicing conjugations
That teacher will eat her apple at home.

그 선생님이 집에 사과는 먹었어요.
그 = The That => 저
선생님이 => 선생님은 is better. We usually use "은/는" for the first subject word.
집에 => 집에서 Sometimes "~에" means same as "~에서". But most of time, it's a little different.

For example.

1. I go to school.  나는 학교에 가요.

2. I'm studying at school. 나는 학교에서 공부 중이에요.

사과는 => 사과를 Apple is an object word, so you have to use "을/를" at the end of the word.

먹었어요 meaning is "ate". "~었어요." is past tense. But you wrote "will eat" in English, so you have to write this word for future tense. "~거에요." is the form of future tense. At the result you can write your sentence like below this.

저 선생님은 집에서 사과를 먹을거에요.