"Is she eating the ice cream?"
Translation:Spiser hun isen?
It can mean that as well, but is often used as a short version of "iskremen".
Is isen a slang for iskremen or is iskremen just not used or rarely used?
She is the subject, hun. Henne is the object form, and in a question like that objects end up last (verb noun pronoun). It makes for a terrifying question but it would have to be Spiser iskremen henne? to be grammatically correct (Is the ice cream eating her?)
That would be pretty ❤❤❤❤❤❤❤ terrifying indeed, and wouldn't really make sense to me, since I don't believe icecream can actually eat. It is a very good explanation, and helped me understanding it. Thanks!