haha I honestly and truly disagree. mid range means the length of her z air, where that'd hit and have us NOT get by you because of our bad hitstun. that to me is mid range, is the place where our tilts would hit, and our second jab, aka the only things we would use (lol minus the second jab) so that, is medium length to me, and that is the perfect range to keep sheik at, she can't get ANY closer or we're ****ed.
The good part is that when they get close (there's no if, it happens,) they've got jab and f-tilt.
Samus can avoid f-tilt locks (or at least not suffer as much as the rest of the cast.) N-air breaks it once you get high enough, of which you can DI to get high enough because of her floatiness. And if Sheik uses jab 2, Samus can DI away and jump out.
Therefore, this limits Sheik to jab 1->followups or just f-tilt->followups.
jab 1-->/f-tilt/d-tilt-->aerial/f-tilt...
Or just f-tilt-->2nd f-tilt-->aerial/u-tilt. (N-air can break this after the 2nd f-tilt at nearly all percentages. Therefore, Sheik may just end the lock early.)
If you know Sheik, this is rather a small string compared to her other MUs.
There's also jab 1 -> dash grab, but if Samus mashes on A, there's not enough hitstun for Sheik to land the grab after jab 1 before Samus jabs. Only after jab 2 can they possibly land a dash grab, but Samus can DI and jump out higher percentages. At high percentages, jab 1 may have enough hitstun alone to chain dash grab, but that's only at high percentages. The jab 1->jab 2-> d-smash still won't work until very high percentages. (D-smash is still fast, mind you. They can kill Samus with that move stand alone.)
However, Sheik's moves are all good OoS too. Meaning almost every approach outside of Samus's missile cancling and z-air can get *****, and Samus being brought in close range. Then, Samus breaks out of close range and attempts to keep distance again. Essentially, it all boils down to Sheik trading off bigger and better hits than Samus.
Anyway, this is what I mean by knowing the match-up. Samus's floatiness decreases their millions of options to only hundreds. (hyperbole, but you get what I mean)
Sheik still wins though. She'll dish out more damage than Samus if the match always stays close range. But if the damage made is equal, Samus has the tools to kill and gimp her and pull the match in her favor.