Anelli grew up in New York and is a graduate of Georgetown University. She became fascinated with the Harry Potter books in 2000, and active in Harry Potter fandom the following summer ... shortly before the September 11 attacks in the United States. She says she was drawn into the series by its underlying message of tolerance and love, which she believes was especially needed as the United States geared for war.

In 2001, Anelli joined the all-volunteer staff of The Leaky Cauldron, a relatively new web site devoted to the Harry Potter universe. On her own initiative, Anelli began contacting individuals at Warner Brothers, which was producing the Harry Potter films, and at Scholastic, which published the Harry Potter books in the United States. It took a year before the movie studio took her seriously and began answering her questions with reportable information, and a longer period of time before the publishers agreed to do the same. By the end of 2002, The Leaky Cauldron was receiving over 500,000 hits per day. By November 2008, largely under Anelli's influence, the site became the second most popular English-language Harry Potter fansite, with over 1 million hits per day.

In 2002, Harry Potter author J.K. Rowling announced that she would release a single index card containing 93 words that were clues to the content of the unreleased fifth novel in the series, Harry Potter and the Order of the Phoenix. The index card would be auctioned, with all proceeds benefitting Book Aid International. Anelli organized a campaign to have fans combine their money to purchase the card. She incorporated a nonprofit organization, Leaky, Inc., and became its first president. The card sold to an anonymous collector for $45,231, over six times the reserve price. Leaky, Inc. donated the $23,656 they had collected to Book Aid International. In 2005, Anelli established a for-profit entity, Leaky Net, LLC, to serve as the legal entity representing her TLC website business. It is a private limited liability company registered in the state of New York, where she currently resides (as of 2009).

Rowling praised Anelli and The Leaky Cauldron on her personal website in May 2007. Anelli had instituted a strict policy against spoilers of the seventh book, saying, "We just don't want someone taking what J.K. Rowling has earned away from her, which is the right to tell us where these mysteries end." Rowling agreed, saying, "I want the readers who have, in many instances, grown up with Harry, to embark on the last adventure they will share with him without knowing where they are going."

Exclusive interview

In 2005, Rowling personally invited Anelli and Emerson Spartz, the teenage webmaster of popular fansite Mugglenet, to Edinburgh, Scotland for the release of the sixth book, Harry Potter and the Half-Blood Prince. The two were granted an exclusive interview with Rowling the day after the book was released. The only other interview Rowling granted that weekend was to a group of 70 children, aged 8–16, who were selected in various contests for the honor. Anelli and Spartz were the only Americans included. The pair published an extensive, three-part interview on their respective websites. The interview caused some controversy within the Harry Potter fandom. At one point, Spartz referred to fans who believed that characters Harry Potter and Hermione Granger would become a couple as "delusional", and Anelli and Rowling laughed. Both Spartz and Anelli received a large quantity of hate mail from fans who believed they had been insulted. One adult fan remarked that, "It was like Melissa and Emerson were our representatives, and you don't want to hear your ambassadors be so partisan. You hope that they're speaking for everyone." Anelli later commented that the irate fans had "lost the ability to divorce themselves between what J.K. Rowling is doing and what they'd like to see happen, and they've taken their disappointment and projected it onto her. I can totally understand how you could be upset if your preference didn't happen, but I can't understand or tolerate that people who claim to be her fans can be so mean to her."

PotterCast

Anelli also serves as a host of PotterCast, a Harry Potter-centered podcast sponsored by The Leaky Cauldron. Episodes of the podcast average 30,000 downloads. The shows attract a slightly older audience than other Harry Potter podcasts, partly because its hosts are older, primarily in their twenties and thirties. PotterCast focuses primarily on news tidbits, with some celebrity interviews.

Warner Brothers invited, and paid all costs, for Anelli and Andrew Sims, host of MuggleNet's podcast MuggleCast, to visit the set for filming of Harry Potter and the Order of the Phoenix.

The show has interviewed many people integral to creating the Harry Potter books and films, including actors, directors, book editors, and author J.K. Rowling herself.

Anelli's work at The Leaky Cauldron was volunteer. During the day, she worked to support herself. In 2001, Anelli began working at MTV Networks' Pages Online, a magazine for the entertainment industry. By 2004, she had become a full-time reporter for the Staten Island Advance. Anelli is now a freelance journalist based in New York City.

Her first book, Harry, A History was released in early November 2008 and debuted at #18 on the New York Times Best Seller List. It tells the story of the Harry Potter phenomenon through a superfan's eyes. Harry Potter author J.K. Rowling wrote the foreword.

Tim Cornwell in The Scotsman explains that "the book captures the flavour of Pottermania, where fans' e-mails fly...with the latest breathless news of the writer and her progeny." Another review in the same paper, by Ernie Waters, says, "Anelli unravels what lies beneath the Harry Potter phenomenon and how it feels to be so wrapped up in the mystical world. ...Crammed with details and facts, from Harry Potter's struggles with Voldemort through to Rowling's personal life as she developed her adored characters, this is a heartfelt, well-written book by a true insider. ...It tries, and largely succeeds, to explain just what it is about the boy wizard which inspires such deep-seated devotion."