^
Jack (sorry - I have to distinguish her from Jac Monika ) hasn't been mentioned because she isn't a "shortie" of Cara D, Hannah Holman proportions..
She's shorter than alot of others but not significantly so.
Sigrid is 177, so she's actually nearly 5'10". She isn't a shortie by any means. Jack is 5'8", she's
about the same as Anna Selezneva and Anabela Belikova.
That photo backstage at Dolce & Gabbana is a funny one but I think it's about right. The fact that Jack is slouching slightly and Alana is standing up straight has to be appreciated. (Don't disregard slouching, it lowers height significantly)
Alana is 5'11" solid (180), she isn't 6' but regardless, there's still a difference.
If Jack stood up
properly there'd be about an inch difference there.......deduct the height she's gained in those heels against Alana's about 3 inches compared with Alana's 1" and you have it about right....
Standing flat foot next to each other, there's about a 3" difference between Jack and Alana (5'8" to 5'11").
Also, when talking about girls in heels, alot of people forget that
the actual height of the heel is not how much taller you're going to be because of the way the foot sits in the shoe.
For example if you're in 5" heels, you'll gain 3" height max but if you're wearing a flat platform, for example a 3" platform sandal where the foot is still flat, you'll gain the height of the heel/platform - if that makes any sense at all

So even though JacJab is wearing 5" heels with Sigrid, she has not gained 5" in height (i.e. she isn't now 6'1" in those shoes).