You sound like a very wise person, and it's always refreshing to read an email from someone like you. At fourteen, you can get yourself into all sorts of bad habits, but it's much harder to swallow your pride and come to terms with the idea that you need help to get OUT of a bad habit. This is a good sign. :) If you focus on recovery, you're going to make it.
We totally understand your hesitance to tell your grandmother about the hydros. Who would want to tell their grandmother something like that? Plus, you've seen how upset she got when she found out you were smoking. However, there's a big difference between grandma "finding out" and you actually offering a confession.
She isn't going to just find a bunch of hydros and yell at you. You're actually going to tell her the truth and ask for help. She may not have the same reaction she did when she found out you were smoking. It's always possible she'll be disappointed or shout out, "What were you thinking?!" or something, but those are the kinds of reactions loved ones tend to have for each other sometimes. Don't sweat it. Your grandma wants the best for you.
You could even print out this whole email correspondence and just give it to her. If she needs to talk -- for any reason -- we'll totally listen. We're here 24/7 at 1-800-448-3000.
We hope this helped a bit. It won't be fun to talk to your grandma, but it'd be worse to become a slave to opioids.
Take care of yourself!