I think she only did a half way job, with all the lint that was showing I'm sure there is a lot more down in the machine and like others have said the vacuum attachments are great for getting down in there and giving it a real good cleaning. I also agree that she should have removed the bobbin piece as well. Always dust bunnies under there.
As she said, "she only spring cleans" but with all the sewing that goes through a machine run 10 hours a day, someone else must be in charge of the regular cleanings.