My guess is that at age 14 she has done research and knows what she wants/needs. I suggest taking here on a trip to Joann’s or whatever local fabric and notions shop you have locally. Let her show you some items she is really interested in and excited by. Then you can make notes on items and prices of things you want to come back and purchase.
Edited to add a link to this book which I think would be very useful and help break patterns down in an easy to understand way: https://www.amazon.com/Sewing-Book-ALISON-SMITH/dp/0241313635