@CoachC and/or anyone else out there with this info…are there songs/shows out there that specifically require a belt vs a mix? I’ve noticed the lines being blurred a lot recently especially with new musicals. We don’t want to get down the road with certain audition material only to learn that her choice really should have been belted. Any examples would be greatly appreciated!
Belt and mix are pretty nebulous terms throughout the industry. Physiologically, almost all belting is mixing to some degree, so what people are generally talking about when they distinguish between mix and belt is how “chest (voice) dominant” any song is. Most pre-1960/65 belt songs are very chest-dominant (think Ethel Merman-style, although not necessarily her vocal quality, OR a charactery sound like the typical Adelaide in Guys and Dolls). Contemporary musicals have many different types of belt/mix sound expectations, depending on composer and/or original actor and/or type of character in the show. It sounds from your post like your D is a mixy belter, so the best way to find pieces that really suit her on your own is to scour youtube for performances by singers who sound like her - Laura Osnes, for example, has a very contemporary but most often very mixy belt, which lovely and powerful but different from someone like Sutton (who generally has more chest quality in her belted “money notes” than head quality.)
^^^^^^^ <3 <3 ^^^^^^^^^ THIS ^^^^^^^^^^ @CoachC, thank you! I tried a few times to craft an answer, but it was not clear, so I took a step away to rethink. Now I do not have to :). I always tell my students that "belting " is not synonymous with “pulling your full chest voice up as high as you can… it is all mix to some degree. what changes is the balance between chest and head, and the vowel modifications as you go higher and higher.”
Thank you both very much!!! This is incredibly helpful. At first I thought it was a dumb question and no one was going to respond lol. So I appreciate both of you the taking time. 
Not at ALL a dumb questions - in many ways it is THE question for female singers in the MT world (and that includes those who are already working)!