size charts published on the web so look those up for the best sizing as it will be brand specific. Wheel diameter is a tricky metric for kids sizing too because ultimate tire diameter varies with tire width. For example, a 24”+ tire could be the same diameter as a 26” standard.

For the Vitus 24 the recommended rider height is 4’-1” to 4’-6” and the Vitus 26 is 4’-5” to 5’-1”. So for that particular bike she’d still be on the 24 strictly by the numbers. However, fit for kids is difficult because, as you know, they grow so fast at that age. She’d probably only get one season out of the Vitus 24 and it may be a little small by Fall. If she’s pretty comfortable on a bike already I’d get the 26, expect it to be a little big this year, and plan to get a few more seasons out of it. YMMV. I can’t speak for the other models you’ve listed, but the Vitus is an absolute dream for a kids mountain bike. Here's the link for the Vitus Nucleus 26 if you'd like to take a look: