Her vocals were not "flat", her vocals were weak. "Flat" means below the center of pitch. And her vocals were on key for the most part tonight. The main problem with them is that they lacked power. Her vocal cords are not strong, so her voice lacks resonance and power, even when it's on key. ATRL, not all bad vocals sound bad because they're off-key. A singer can sound bad while singing on key.
What makes me still stan for her despite the weak vocals is that she makes better music than 95% of the current pop girls despite lacking severely in vocal talent. Look at Ariana Grande, vocally talented, yet ultimately produces music that is bland for the most part, averagely-written, and lacking in emotion. With that vocal talent of hers, she should be making better music than Taylor, and she's not. So I've just come to accept that she's never gonna be a strong vocalist and learned to appreciate her for what she is. A good writer and producer and an average vocalist.
The lack of reading comprehension. 
Not sure who looked more bored, the audience or her. Giving Selena Gomez a run for her money with the vocals.
JLo's desperation for a hit is quite sad, she doesn't have a solo hit since 2005 poor dat
