Well, we need to recognize that this was Ms Abrams first novel. Apparently she did what a lot of first writers do – any suggestions, advice, or criticism has to be addressed and fixed! And yeah – after all those rewrites based on what so many different people told her she should fix, it’s no wonder it was a hot mess by the time it got to the agent.
As to hiring an editor from the agent’s list, that makes sense – the agent has worked with the people on the list, knows they’re both knowledgeable and won’t rip off her clients.
I guess my concern with writers wanting to hire an editor of any sort prior to submission is that they oftentimes sound more like they’re trying to hire a co-writer (or worse, a ghost-writer) rather than an editor. Not saying that’s the case with anyone in this thread, of course, but I’ve seen it often enough to make it a concern.