This user has everything in preferences as “watching” or “tracking” , and still isn’t getting the email notifications. They are not going to spam.
Hello and welcome @Giovanni_Lignarolo1 
Have you checked the email logs on your site to make sure they’re being sent? (/admin/email/sent and /admin/email/skipped)
If they’re being sent but not received you may have to check your email provider to see if something is getting stuck with them.
Is the user logged in? By default you don’t get emails for things you’ve been notified about online.
User says she is getting 90% of notifications despite having watching turned on. She is getting emails but not all of them. Depends on the category.
Have you checked /admin/email/skipped?
EDIT: Sorry. That already got suggested. 
Oh, but you didn’t say that you had checked there.