Are you saving her as both a pcs and a pac? Sheik needs both, since she's a transformer. Though usually that doesn't freeze until you're in-game and try to switch.
Every time I've had a hack that crashes at the stage select screen, it's always been a file size issue. Dropping the texture res a notch usually drops the file size enough to work. It does seem odd that your file would be over-limit considering you only have one other texture. But I see you have edited the model. It's possible when you exported it to a .dae it didn't compress as much as it should have, and you might have gotten an unsually large file. Did you triangulate her before export?
Shot in the dark, but what's your file size looking like? Whether a character loads or crashes is usually an issue with file size. It's the character's file size, plus the size of the character's FitMotionEtc (explaining why the mod would work with one moveset and not the other; Project M probably has a smaller file size.)
Don't quote me on this, but I think Zelda and Sheik share total file size, too, so a smaller Zelda file can allow a larger Sheik file size before crashing, and vice versa.
Also, I know this is HORRIBLY late. But about Missingno.... I had a random idea for alt final smash eyes...
What if his colors changed to look like Yellow Version Missingno.? (Ignoring the white there.) Would be kinda fitting, since this one is MUCH more buggy, often crashing the game and whatnot.
Anyone else is welcome to do that. I've got other stuff I'd prefer working on.
I've edited the UVs on Strange. Hope that's cool. His UVs were laid out terribly. It's like whoever made him just ran it through an auto-map program and called it a day.
any possibility of you recording yourself in some of your future custom models?
You mean like record the process I use to make models? I don't do it all in one sitting, though. And I'm constantly pulling up the internet to Google random [censored] while I work.
My bad. Don't know how I forgot that. I added the Fitmotion to the zip.
As far as the Hurt Eyes go.... I think it's the PSA. His normal eyes are rigged to the HeadM visibility bone, the hurt eyes to the OuchM bone. With Lucario, HeadM disappears when OuchM appears, but in the Mewtwo PSA... it doesn't.