Also not to pile on, but she truly seems like one of the nicest people and is very transparent about her reasons for rejection on her Twitter (she talks about the word count and why high word counts are difficult).

Also, she has recently signed two authors who have worked at 140k and 150k. So, if honest, she is better than most; I think the magic words are standalone with series protentional. One of her authors signed a three book deal. But the first one is a complete story in its own right.

@TiagoResende not to pile on, but general advice is also that it's harder (not impossible, but harder) for querying authors to land an agent with a series as opposed to a standalone, and it has nothing to do with the books being prewritten. it's because if the first book doesn't sell well and they don't publish the rest of the series, then readers of the 1st book will be unsatisfied by the lack of conclusion to the full story. some agents are specifically looking to sign authors who have series in the works, but generally, lit agents are looking for strong standalones of a modest word count. Or books with 'series potential' but that can standalone without compromising the story. as sdtsanev said, publishers don't like massive word counts from anyone but authors with a track record of success.

TiagoResende, it's not the agent's job to break your manuscript down into arcs. The entire industry is skewing toward shorter works and debut authors no longer have the luxury of massive word counts (except in extremely rare occasions) until they have a track record of success. And barely anyone is getting personalized rejections anymore, so to be angry at any given agent for not going out of their way to analyze the structure of your manuscript and give you feedback on it, will severely limit your querying options in the future. If your book is that easily split into smaller books, consider querying only the first of those. If nothing else, you will no longer trip auto-reject filters based on word count. And I'm saying this as kindly as I can - you will get much further in this thankless and unpleasant process if you try to not take rejection personally.