Several times, when answering a question sentence in English, if the words "Do" or "Does" are left out, it is marked incorrect. This should be corrected. "The boy eats with you?" is understood as a question.
If I would like to say: "Is the child ( singular without a spesific gender) eating with you," how should I say that?
Most people would use the male form ילד if they don't know the child's gender; hence, if you use ילדה it's strongly assumed that you know it's a girl. But that doesn't mean ילד is gender-neutral. If I ask you הילד אוכל איתך but this is actually a girl, you'll feel that I made a mistake and probably correct me (כן, אבל זאת ילדה, רק שתדע).
The way to be gender-neutral is cumbersome, but in some contexts you'll see it: הילדה או הילד.