This is a hard counter matchup. Poppy is designed to stop champions with dashes, and your entire kit relies on and . You must play a patient bait-and-switch game to survive and find openings.
Poppy is the ultimate Riven counter because her stops every single one of your dashes. This is a survival lane where you must play patiently and wait for her to waste her cooldowns. You cannot play aggressively unless you know her anti-dash utility is unavailable.