How to counter Samira
Let us take a look on how to beat Samira. We will look at champions who are strong against Samira and who are weak against Samira. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Adc champion who counters Samira. You can already win in champion select with the right counters for Samira. If you want to know how to counter Samira then you need to take into account the best picks vs Samira and the worst picks vs Samira. This Samira counter data is based on matches played by Pros on patch 14.22 and previous ones. It is important to see whether Pros counter picked Samira or whether they played as Samira.
Champions used by Pros to counter pick Samira
Looking at the matches from Pros (see table Pros counter picked Samira) we can see that they picked 
Kai'Sa most often to counter pick Samira. The matchup Kai'Sa vs Samira occured 25 times. Samira has 12 wins and 13 losses in this matchup. Learn how to counter pick Kai'Sa to get another perspective on the data.
Lane outcome for Samira
When looking at Samira counters you will notice that win rates alone are not conclusional. Therefore we provide an overview (see table Lane Outcome) where you can see the lane outcome of Pros who played Samira. The lane outcome of Samira consists of three outcomes: Win, Loss or Draw. Let's take a look of Samira lane and match outcome for specific matchups. Considering the lane outcome and the match outcome of a specific matchup, might enable you to find the right counter for Samira.
Conclusion
Analyze the available data and learn how to beat Samira. To master Samira take also a look on Samira builds and runes for Samira. Good luck, Summoner!