Oh, I tried this method too a while back! This spell got some use after all, so I'm here to report my findings hehe.
As a preface, I used a mod called "More Reactive Companions" and, with a little tinkering, this achieves two things:
1. Minthara will always react to everything first.
2. Upon interacting with an object, instead of Tav or Durge, Minthara will be the one making a comment about it.
With this mod, I discovered Minthara has a reaction to almost everything in Act 1, but there's a catch: 99% of her dialogue are duplicates to Tav or Durge (unlike other companions, who have unique lines) and those same duplicates are mostly
unvoiced.
As it's been pointed out above, she has several voicelines in the creche. This does not apply to the Underdark or Grymforge, sadly, all of her overworld lines there are mute - unless I missed something.
There's a voiceline here if you interact with the wheel
as Minthara.
And here when you simply pass by.
And here. Tav or Durge also says this, so it's not unique.
This one, however, is unique. She has a reaction to what happened with Vlaakith. This is pre-patch 6 so it's not replaced with the Emperor line XD
I made this meme with a picture I took of her at the Creche, very productive as you can see.
I'm assuming what's left of her lines are simply residues they haven't been able to clean up yet. With all that said, I did almost 90% of Act 1 with Minthara and I can say I very much enjoyed it. Her presence is enough to enhance my experience lol, so yeah. Thanks for reading :3