Javascript/canvas? It's easily transferable, libre, and easy to distribute whatever she makes to her friends. Downside is that all the tutorials make it more complicated than...

// Treat this part as a magic incantation for now.
document.addEventListener("DOMContentLoaded", () => {
  let canvas = document.createElement("canvas");
  canvas.width = 256; canvas.height = 256;
  document.body.append(canvas);
  let ctx = canvas.getContext("2d");
  let keys = {};
  document.addEventListener("keydown", function(e) { keys[e.key] = true; });
  document.addEventListener("keyup", function(e) { keys[e.key] = false; });
  // Initialization code here
  let x = 128;
  let y = 128;
  // End initialization
  setInterval(() => {
    // Game step code here
    if (keys.ArrowLeft) { x -= 2; }
    if (keys.ArrowRight) { x += 2; }
    if (keys.ArrowUp) { y -= 2; }
    if (keys.ArrowDown) { y += 2; }
    ctx.fillStyle = "#000";
    ctx.fillRect(0, 0, 256, 256);
    ctx.fillStyle = "#F00";
    ctx.fillRect(x, y, 16, 16);
  }, 16);
});

Just chuck that into an empty HTML page and you should be good to go.