Well the child wants to know what part of Christ was in the host, i.e. the eye, skin, arm, etc. After she was told all of Christ was in the host she wanted to know how he could fit in there. This child has already received her 1st communion.
Now you are getting into specifics.
The first of these questions was answered somewhat awkwardly (that Christ was “in” the Host) which set the table for the child’s next logical question: How could he fit “in” the Host??"
A better answer is that Jesus is
Really Present in the Host. That means that he isn’t inside of it, but it
becomes him when the priest says the words of consecration. It still *looks *like bread and *tastes *like bread – but Jesus is really there.
The** “how”** part of the question is a whole different thing. Adults ask this too, and the answer is the same for them as for this little girl –
we don’t know.
When it comes to the chief mysteries of the Christian Faith which involve the direct action of God – the Eucharist, the Incarnation, the Trinity, etc – “how” is not an answerable question. We --children as well as adults – need to learn to live with the idea that not everything is qualifiable or quantifiable by empirical evidence or simple logic. Some things are just transcendent mysteries, and that’s OK.
I’d further suggest your friend invest in a Baltimore Catechism and go through it with her daughter – a lesson a week if possible. My extremely bright twelve year old boy is being raised on it, and he can run theological circles around most Catholic adults.