I (USC) am older than my Egyptian husband by 12 years. We are of the same religion, however. (I converted in 2008, long before we met).
I do feel the age gap is a red flag. However, the larger red flag is hiding it from your family. It's the same as lying to them. Especially after four years. Were you planning to hopefully be approved and just fly away?
I do feel it's also a red flag if she did not insist on meeting and gaining the approval of your family. Anyone who has researched even a bit of the Egyptian culture knows how important family approval is, and I think the consular knows this as well.
My advice, have her meet your family in person as soon as possible and submit bonofide evidence such as photos of them together, chat logs between her and them, etc.
Wishing you the best.