Whiteley Houston's version was actually prerecorded, but she did sing it live when recorded in 1 take

Lady Gaga also did a very good version

Agree that with this girl in the OP, that the song (which is challenging) was just out of her range, plus she's a "cursive" singer like that girl in The Chainsmokers or Ellie Goulding, which is not a very good technique for singing IF you want range, flexibility, versatility, or even longevity in your voice. In general she's a decent, consistent singer (I've seen many videos of her performing live since this) as long as she's within her range. I think she just lacks the skill for that song specifically.