I saw a recent post on FB about this very thing. What the owner did was remove the top shelf of her new very tall cat tree until her cat had grown a bit, based on comments suggesting that. My contributing advice to that thread was to also add some sort of cushioning, pillows or padding below the cat tree, which is what I do here for our 7' tree since we have wood flooring, but I am a worry wart, anyway.
I think if you get a tree that has removable posts, you could do the same for Elsa? You could also position the tree so another piece of sturdy furniture is nearby for landings from the tree, rather than the floor. Elsa will most likely learn quickly the best way to manuever up and down any tree...and be sure her nails are not trimmed too short so she can get a good grip while climbing.
I would think for Elsa's size at this point in time, a tree of around 4-5' tall would be sufficient, and if adjustable, you could add the rest of the posts at a later time to make it taller as she grows....of course, you could always start out with a shorter tree, and add a taller one later...Elsa will love you for that!