It sounds like, if that timely manner is at least a day long then she'd get it done reliably. I think the only issue you could possibly see here is one of labour exploitation if she was sending the work off to someone else - it might be that she specifically shouldn't be paid but you as a company would really like to get in touch with whoever is on the other side.

Or it might just be that some people are introverted and crack under pressure whenever the spotlight is on them but, once they have quiet time to themselves, they can really power through problems.

The description of the scenario isn't nearly enough for us to get any grip on what was going on without making some huge assumptions, but the facts that we have are that she tended to really struggle when coordinating with coworkers and that she completed the work expected of her - there could be numerous explanations and the observations from the poster might even be inaccurate.