Uthrow-uair actually used to work on a lot of characters to sky KO at very low percents. Mario, Ness, Lucario just to name a few.
If you can't DI her bthrow, I don't know what to say. With proper DI the bthrow still sends quite high giving you more than enough wiggle room to recover, even as a fast faller. Her grab is always relatively difficult to land. Frame 11-12 is as slow as it gets for non-tether grabs. By comparison, almost all other non-tether grabs are 6-7 frames. She won't be shield grabbing much if you space your aerials properly and don't subject yourself to huge frame disadvantages, and her aggressive grabbing is hurt by this, as well. You really need to outplay your opponent to get a good number of grabs with her. Her bthrow's KB is not stronger than her Fsmash.
Zelda is just good against aggressive playstyles, like those a fast faller would utilize. She's also great at comboing them. However, she is straight up awful against camping and defensive playstyles. As effective as her combos are against fast fallers they all outspeed her severely and give her a hard time when they don't just jump fearlessly into her (Usmash) range. Better idea, don't use a fast faller against her. There's really only three that fall into the best combos she's capable of, and there are plenty of characters better than her who don't fall into Usmash destruction. In other words, play smarter. I highly doubt you play Zeldas other than me who will abuse all that against you, and that's online of all places.