Barry was talking to Oliver about his metahuman powers. Of course you were spying on them. Apparently you can clone powers, but Barry doesn't trust you. You and Oliver are friends, so you knew his identity... and now Flash's.

✧

As soon as Oliver left, you swallowed hard and tried to leave without being caught, but Barry uses his speed and pins your arms above his head, against the wall.

— "What are you doing here and why were you hiding?!" -His voice sounded stiff, but not hostile.