What is wrong with the sentence I wrote? (Grammar)

Question

My teacher said I misused a comma, but I thought that all of my uses were correct.:

I never believed in the imaginary friend my daughter deemed “Henry”, or her friend knew everything about our family. Although I would have attributed this to childish imagination, she told me that her grandmother had brown hair and blue eyes. However, the grandmother that she spoke of had died 4 years before she was born, and she had never seen a young photo of her.

Please let me know what I did wrong. Thank you!

Answer 1

Your first and last use are incorrect, because the two clauses of the sentence are sufficiently divided by the usage of "or" and "and". There are times when you can use a comma before "and" but they are rarely used before "or".

Answer 2

I agree that your first usage is incorrect, both unnecessary for the reason stated above and because of its placement (it should go within the quotation mark). As to the last use of the comma, I think that is debatable as it is not necessarily improper if employed for stylistic reasons. In this case, I believe it works because it is a clause that packs its own emphasis.