Also, if it's any use, sheik's feet on dsmash are invulnerable on the first frame the hitbox appears, so if you both would dsmash at the exact same frame, it would either clang or you'd outprioritise her dsmash (dunno how invulnerability affects the clanging). Space outside of her shieldgrab range with fair, which also causes enough shieldstun so that you can grab her with your longer reach, jab once or twice and then grab her or tilt/smash her ect. Dthrow at 100% will pretty much KO peach, from both fair and uair (if you play NTSC and not Pal) and sets up nicely for sheik's aerials and tilts on any %. So abuse that grab a lot. Your jab hits on the second frame, but Peach's jab is also 2nd frame attack and has nearly as much range as your jab has, if not the same.