Sheik v. Samus
Long-Range
If you're a good needle camper, Sheik wins. Samus's camp game revolves around short hopping, and missiles do no good when Sheik can needle cancel into shield while racking up free 2-18% damage. This is of course assuming the match is played on flat terrain. If it's angled, then it's within Sheik's best interest to not needle camp. But that could be said with every match-up for Sheik.
Mid-Range
Samus wins. There is still significant lag time when needle canceling on the ground, thus we're more than willing to trade the 4/7% z-air and knock off Sheik's silly needle game. Our f-tilt outranges your f-tilt and our d-tilt comes out in 6 frames (Sheik's f-tilt comes out in 5, jab in 2, I know, but when d-tilt does 14% fresh damage in that short frames with a fairly big disjointed hitbox, not to mention at low percentages, with Sheik being lightweight and a fast faller meaning easy follow-up options for Samus... it's not something to look over.)
Sheik cannot emphasize on shield dashing enough when approaching Samus. Once Samus gets into z-air range, Sheik has to switch from passive (needle camping) to aggressive methods, or else Samus just racks up damage. If the Samus gets too predictable, DACUS underneath the z-air/missile cancel for some damage. If you get too predictable, Samus will chain all sorts of shanningans from z-airs and missile cancels that it's not even funny.
Close-Range
Sheik wins (crowd roars for Sheik.) F-tilt locks are disrupted by our n-air though, and because Samus is floaty, it's very easy to avoid the lock. Therefore, it would probably be best to not rely on it and rather finish up with u-tilt/n-air/f-air. Another important mention is the jab 1--> jab 2-->d-smash kill set-up will not work until very very high percentages. The hitstun doesn't last long enough, and Samus, floaty as she is, can jump out of range from the d-smash.
Other important facts... Samus's pivot grab is beastly. If you get too caught up in your aggressive ground game, expect the Samus to retreat and grab you. (Directed to you Light. Watch out for this when you face Xyro at HOBO.) Otherwise, most aerial approaches Samus has close range (d-air, maybe the occasional sh ff u-air->up+b) are beat out through shield grabbing and OoS n-air. Cool fact to mention, if Samus approaches with d-air and you shield, you may be able to pull the chain out for a good 5% or more, given that you predict the buffered spot dodge. (I'm just telling you guys how to beat Samus, lol.) If we buffer a jab instead, your shield grab *****. RPS anyone?
Also, lol at rolling. Don't. Backside of Samus's d-smash easily set-ups for a follow-up f-air at low percentages, z-air at high percentages. Not to mention it does decent damage and has good shield stun/knockback.
Air
Actually, I'm going to call this even. Both characters suck if they find themselves on top. Sheik's fast fall helps mitigate any follow-up issues from Samus, but f-air's hitboxes last a while, so a well-read air-dodge spells **** for Sheik. Or, Samus can dash grab/pivot grab your landing if you've exhausted your second jump. Likewise, Samus's floatiness is a curse, but bombs and going for the ledge lower Sheik's options for following up as well.
Ledge-game
Samus beats Sheik. Especially on stages like BF and SV. At the same time, roles reversed and Sheik is recovering, Samus's u-tilt has rather deceptive range and power, easily a kill move at 110% if hit in the air. Xyro doesn't use bombs as far as I'm aware when edge-guarding, but most other Samus mains will. This, on top of u-tilts start-up time, will almost cover all of Sheik's invincibility frames. Almost. Switch up your recovery from the ledge (as a good player, you should be doing this anyway) and you should be fine. For the non-bomb users, they'll try to intercept with n-air/d-air.
Recovery
You're going to get gimped if your not intelligent. End of story. Samus chases you, or tether hogs you and you're leveled with the stage, you're done. If you have to vanish onto the stage and fail to cancel landing lag, Samus's b-air from the ledge knocks you off and starts the process all over again. When momentum canceling, be wary of whether you absolutely need to use that second jump to cancel the horizontal knockback, or if your FF'ed aerial does enough. That second jump can make all the difference.
Overall
60:40 Sheik's favor.
Passive-Aggressive style recommended. Be cautious when recovering, and try not to compete with Samus's ledge game. Close up and good reads win you the match.
*Even though numerically, with everything I listed, Samus has more advantages than Sheik, also realize the majority of the MU will be played in your advantage zone. (long-range/close-range) In other words, give different amounts of weights toward them and Sheik still has a significant advantage.*
FD is a great CP against Samus. BF, things can go even. RC is an okay CP, but that depends on whether or not the Samus is comfortable on that stage tbh.
GL to you Light. I want a replay of the set you guys play please.