Can you check her over really well for injury since she had an encounter with a fox?
I agree, it looks like her crop is not emptying.
Check her crop in the morning. If it's not emptying, then treat her according to this article, but you will want to adjust (increase) medications/oils to accomodate her size since the article was written for chickens.
I would not withhold food/water, nor would I vomit her.
She's never laid eggs in her lifetime, so it's doubtful she is egg bound now.
@casportpony may be able to give you better suggestions.