I got it! Anyone remember Fluttershy can do the same thing.(Who Doesn't?) Turns out both of the two bear enough 'Cute' within them that they have Weaponized it.( Didn't you see that coming?) But this raises questions.(Always does) Would it be effective in Crowd Control? How Dangerous is said weapon? (what good is a safe weapon?) What would happen if both did it simultaneously? Any Ideas?
I finally understand now so this is what happened:
Scootaloo was cute and everypony who saw her face had a heart attack,when Rainbow Dash heard the CMC,she went down to see what was happening,and then Rainbow Dash got a heart attack,and Scootaloo got her cutiemark but she wasn't happy with it.