The evidence they present for that is that she wrote a python library to interact with their websites (or in their words "developed a repository for a python module for interacting with OCLC's WorldCat(r) Affiliate web services"). Also that she worked for a competitor, describes herself as an archivist, and has publicly stated that libraries and archives should be open and publicly available.
It's not exactly convincing evidence that she's involved with Anna's Archive IMHO.
Her name (Maria Dolores Anasztasia Matienzo) even contains the letters Anna (almost), so she must be the mastermind behind Anna's Archive!
Her library is the top search result if you search for WorldCat in github. Though I personally would have gone with bookops-worldcat, since they claim they made major changes to the library to account for 2020 API changes in WorldCat.
Really not thrilled to see an organization which claims to represent the interests of libraries stepping so hard on freedom of expression to write software. Pretty shameful.