3D modeling software: TinkerCAD 3D-> https://www.tinkercad.com/.
This website is free, can be used on a tablet, computer, or phone. I wouldn’t use it on a phone personally because the screen is too small, but it is possible. She needs an account to use this website
Here is a 9 minute video explaining how TinkerCAD works -> https://www.youtube.com/watch?v=gOs6Mdj7y_4
Here is another 9 minute follow along video for a part you can create -> https://www.youtube.com/watch?v=24ByEWUmJ3g