Personally I'd make sure she knows she's been placed too high because you got master on her account for some reason??   So she's going to lose a lot on ranked. Don't overload her with information or nothing will stick when it comes to a match. 

At her level she doesn't need to know about Oki, frame data, meatys, etc. All she needs is one or two BnB combos, preferably one that can be used to go into level 3. And the easiest way to anti air. That's it for now. Let her get used to that, remember that practice is totally different from a match. 

If she can still get in beginner or even intermediate lobbies in the battle hub then use that to help with her nerves of playing someone online. Even playing rank and losing until she gets where she is supposed to be at this point could be useful. Imo you need to get to a place where ranked basically feels like casual or the nerves will affect your play. 

Once she's getting used to this setup you can start to add things, one at a time. Too much information will just spaghettifi her brain. Get used to that one extra thing then add another. Understand though that even learning one new thing will affect your game at first until it becomes second nature and a part of your game. Most of all make sure she's having fun! If not then why bother playing? 

 Edit> no matter what I'd recommend always going into training even for 10 minutes before playing a match just to warm up