What kind of questions are asked by an immigrant official at port of entry to a visa waiver?

this is very subjective. As long as she looks really innocent and harmless, usually its ok. What customs officers are worried about are terrorist or like those china or india immigrants who might stay in their countries longer than expected. Maybe you can write a note for her to explain that she cant speak english and that if anything they want to ask her, they would need to get a translator.