
Reviewed for patch 7.3b

Favorable matchup
Reviewed for patch 7.3b
Samira has to get close and chain different hits to reach the S rating that unlocks Inferno Trigger. Caitlyn punishes her from range on every last-hit, places traps where Wild Rush ends, and uses the net to regain the distance Samira just closed.
Daredevil Impulse ranks up when Samira alternates different attacks and abilities on champions, and Inferno Trigger can only be cast at S. Caitlyn's range lets her hit on every last-hit without giving Samira nearby targets to build that sequence.
Wild Rush carries her through an enemy to the other side. Yordle Snap Trap immobilizes and reveals the champion who steps on it and sets up an empowered Headshot: place it behind you or next to your support, where her engage usually ends.
While Samira spins with Blade Whirl, your shots are wasted: the ability destroys enemy missiles. Cast Piltover Peacemaker while she's spinning and you lose the shot. Wait for it to end and punish the cooldown.
Punish every Samira last-hit from max range. When she comes in with Wild Rush, answer with 90 Caliber Net to get out of her reach and wait for Blade Whirl to pass before using your skillshots.
If you're playing Samira, don't look for Style against Caitlyn alone: you need your support to immobilize her first, because your attacks on an immobilized target bring you to her. Force the engage once she has used 90 Caliber Net and keep Blade Whirl for Piltover Peacemaker. Check where her traps are before you Wild Rush toward her side.

Favorable matchup
Reviewed for patch 7.3b
Samira's engage depends on Wild Rush, and Flame Chompers interrupts dashes and immobilizes the champion who steps on them. With Fishbones, Jinx also hits from further away than Samira can answer. If Samira reaches S on top of her, though, Jinx has no escape.
Flame Chompers! explode on contact with enemy champions, interrupt dashes and immobilize them. Thrown on Wild Rush's path, they stop Samira's engage before she reaches your backline.
With Switcheroo! on Fishbones, your attacks gain range and deal area damage. Samira needs to be close to build her Style; every last-hit from that range costs her health without giving her a nearby target.
Poke with Fishbones while Samira is far away. When she steps forward, throw the Chompers between her and you, not on where she stands now. Without Chompers available, play behind your support.
On Samira, your turn to go in comes when Jinx spends Flame Chompers!: until then, any Wild Rush can end with you rooted. Engage from a side angle away from the traps and keep Blade Whirl for Zap!. Once you make contact, alternate abilities and attacks to hit S before her support can respond.

Execution matters
Reviewed for patch 7.3b
Xayah answers Samira's two key moments: she can root her with Bladecaller if she crosses the feathers while using Wild Rush, and Featherstorm makes her untargetable during Inferno Trigger. It hinges on those cooldowns; without them, Samira has the edge up close.
Bladecaller pulls all your feathers back toward you and roots any enemy three or more pass through. Seed feathers with Double Daggers and your attacks, then position so Samira ends up between them and you: if her Wild Rush finishes on that line, the recall stops her in the middle of her combo.
Featherstorm lifts you into the air and makes you untargetable for a moment, while dropping more feathers. Use it when Samira activates Inferno Trigger near you so you don't take those shots, and line up the root for when you land.
Trade when you have feathers on the ground and Samira is between them and you. If Featherstorm is on cooldown, don't let Samira reach S near you: back off until it's available again.
A Samira facing Xayah has to count feathers: don't end your Wild Rush on the line between her feathers and her. Bait out Featherstorm before you use Inferno Trigger, or start your ultimate right after she uses it. Blade Whirl destroys her daggers, so save it for Double Daggers if you're about to engage.