If you keep getting WD back dtilted, just overshoot your aerial and smack her where she will be when she WD's back. If she DOESN'T WD back, she STILL will get hit by your aerial and you'll end up way behind her and can just utilt or run away or whatever your heart desires
And Peach's shield pressure is not even pressure at all. I will give you the frames and then we can all see why it's easy to escape what she will do after a FC nair.
FC nair has +4 frame on block if you shield it. Peach's jab comes out in 2 frames. Okay, you're locked in your shield at this point and cannot do anything to her. So what? Keep shielding. So, After she jab your shield, she cannot grab you before you have time to roll or aerial her back. If she dsmashes, just roll away from it or shield DI out of the range of the attack. If she FC nairs your shield, it's still +4 on block and her grab comes out in 7 or 8 frames, can't remember, so if you don't see her start the jab up, just roll so you can avoid the grab or the dsmash. I forget how fast dsmash starts up, but you can simply roll away from her after she doesn't nair you and be safe. Basically, what I'm saying here is that you should hardly ever get stuck in your shield until you get poked by one of her ******** shield mixups.