Chippy, if you put out an a capella piece, & it wanders off-key like this, then you need tutoring to stay in tune, imho.
I AM a singer, as well, Chippy, I've been singing for most of my life, professionally for over 35 years, & HAVE tutored a few students in voice.
"Hallelujah" happens to be one of my fave tunes, btw, & I sing it, too. Within her rendition, she wanders over a 1/4 tone.
Same with "What I Got," & "Don't Speak" wanders even farther. In her defense, "Don't Speak" is a much more difficult song to sing without accompaniment, but it also points out areas where she needs help to a larger degree.
The breathy comment was aimed at the fact that where a song like "Don't Speak" gets loud & powerful, she holds to the breathy tone, keeping it quiet where it should get louder. A TUTOR would help her in these areas. She needed to open up & let that power out on the chorus. Peter Gabriel does that very well, if you want to make that comparison.
You may think I sound like Simon. I've heard that before. Still, I responded to her request for an unbiased opinion as best I could, within the parameters of my knowledge & experience. I did not address the timing issue, but in an a capella piece, the tempo is more open to personal interpretation.
I was as fair as I could be on the material she presented, & answered her as well as I could. There is a big difference between "wavering," as you call it, & "wandering" off-key, Chippy.
If anyone asks for an unbiased opinion, I think it unkind to give them mere kudos for trying, while withholding actual advice & opinion, like they asked for, if I have them to give. Kind of like what you did, wouldn't you say?
Ooops - I just noted that she asked for a "biased" opinion...okay, forget everything I just said.