You can do a salad with what you have. Do you have any lemon juice? The apples and bananas will get brown if you don't dip them in lemon juice. If you don't have any, just slice the bananas after you arrive at her house, and add it in & toss gently. For the apple, you can do that when you arrive as well. If you want to do it at home, leave the peel on it, cut it in quarters, but reassemble it so the cut surfaces aren't exposed to the air. Wrap in plastic, then when you get there, split it open, quickly cut out the core, and slice each wedge into chunks.
If you have any Greek yogurt, you can spoon some into a glass bowl, cut up and add the mixed fruit, then top with more Greek yogurt. You can add some granola or Grape Nuts to the top if you have it, or take a drizzle of honey and make a little swirly design on top. I think Greek works better than regular yogurt which is a little runny.
I think everyone will be delighted with what you bring, no matter what!