I think M. Russell's claims to have written parts or most of the Millennial Dawn Series are way overblown. They appear in the divorce transcript. The transcript indicates that she edited for grammar. After making claims to authorship, she repeatedly refers to the books as "Mr. Russell's books" - Not at 'our books' or 'my books.' She made her claims in an attempt to gain money, and in doing so made several claims that do not stand up.
When the Watch Tower was new she handled correspondence. Russell sometimes outlined an article in detail and gave it to her to write. She was very much more a research assistant than an author.
Her education is overblown by modern researchers. She attended Pittsburgh High School for one year where Russell took night classes offered through the YMCA. There was little difference in content, though Maria obviously had a better command of grammar. She attended Curry Normal School, a teacher training institute. Modern researchers confuse this with the modern teacher education. [BEd in 4 years; MEd additional 1-2, etc.] Curry institute had several educational tracks, teacher training was one. Course work lasted six months. Maria was not college educated in any sense, and in many respects was an autodidact.