So she had and passed the legally-mandated background check -- and assuming she's not a criminal, and that the background check looks for the right things, that's as it should be.
Her obvious point is that she should have had to do "more" to prove that she had no bad intentions with the gun she'd purchased.
Not sure what "more" she'd suggest ... I guess a waiting period. Which would not really have helped in Orlando, as Mateen had been planning his act of terrorism for some time.
I will say that the fact that Mateen passed the mandated background check is cause for serious concern. There were all sorts of red flags for that guy. Why was he not flagged for this?