I don't know how exactly she made it, but this is a reasonable simulacrum of my mother-in-law's Thanksgiving Dinner Salad.
A packet of orange jello, enough to make 570 ml / 1 UK pint (I used a block of tangerine today)
A medium tin of pineapple pieces in syrup
Apple juice, less than a pint
1.5 large fresh crisp carrots
A clear glass or plastic dish that you can serve from, or a nice-shaped dish if you plan to turn it out.
Drain the pineapple well. Heat the syrup and melt the jelly into it. Make up to a pint with cold apple juice.
Pour a small amount of jelly into the dish and pop it into the fridge until it sets well around the edge. Grate the carrots, not too finely. Sprinkle the carrot into the dish, fill up with most of the rest of the jelly. Adjust the amount of carrot so that there will still be room for the pineapple and the last of the jelly.
Arrange the pineapple pieces on the top, and gently add the last of the jelly. Refrigerate until set, turn out if you like to slice, or spoon from the dish.
You can always make more jelly if you need to, for example if you've chosen a bowl-shaped dish. Don't try to use fresh pineapple, the jelly won't set. You might be able to get away with pineapple in juice, but I'm wary. And if you like to turn it out and make a centrepiece of it, you can put the pineapple in first and add maraschino cherries to make a pattern.