1. The shield can move faster than Orihime can, but in any situation where 2 or more of the fighters attack her at the same time (which is highly possible and could happen to any of the 4 combatants), then Orihime is screwed. The shield can't cover her whole body, only mono-directional attacks. Thus (for example), Sakura could bypass her shield by smashing the ground underneath it and one-shot Orihime, Wendy could blast f*cktons of air at her from all directions and one-shot her, etc.
2. Base Ginjo is 7C
3. Orihime isn't gonna hide in a hole for the whole fight. She's gonna be targeted eventually. But I admit I said some nonsensical stuff
Plus there is no reason for the other 3 to NOT attack Orihime at all, just maybe not initially
4. For Orihime's shield durability, the start of the "chain" of scaling starts with Pre-Timeskip Toshiro, who has a 513.56477 megaton feat, meaning Orihime can casually take 513.56477
For Wendy, she scales to Elfman who beat Ajeel alongside Lisanna, and Ajeel scales to Brandish, who has an effortless 1.2 Gigaton feat (lifting an island)
Half of that (assuming Elfman = Base Wendy = 1/2 Ajeel) is 600 Megatons
So Wendy could smash the shield no problem
As for Sakura, she has her own power-scaling chain, which ends at Taka Sasuke, who has a 600 megaton feat (destrying the Uchiha compound as well as the mountain below it with Kirin)
Adult Sakura should be far superior to Taka Sasuke at this point
So she can also smash the shield no problem
I don't see where you get 657 megatons
5. She doesn't have better AP, but everything else seems ok
6. Move away and turtle up you say? So when the other 3 duke it out and there is a winner, how will she kill said victor? If she tries Koten Zanshun it's just gonna get crushed
Tsubaki got effortlessley crushed by Yammy simply closing his hands around it, thus it's unreasionable to say that Tsubaki's durability is as high as Orihime's.
Her hand-to-hand is not her specialty, so compared to 3 other people who do specialize in mid-to-close range fighting she's gonna get stomped in that specific category. Being a black belt isn't going to help you when the opponent's striking strength are far superior to your own
Sakura's healing is much, MUCH more practical than Orihime's, and is actually useful in the middle of a free-for-all such as this one.
I'll add yor vote though. No need to be so insulting