In reply to ElArt:
I run some coaching headgame workshops for both adults and children; one of the most common things people identify as a psychological barrier to their performance is an aversion to heights, exposure or falling - Ellie is not alone!
There are of course loads of drills and techniques (that can be dressed up as games) that have already been suggested, and as has already been suggested as long as Ellie wants to go higher, then simply doing more and being gentle will probably do it, supported by you being there to explain or demonstrate how/why she is safe.
Something I always focus on with people is to identify exactly where they get scared, then identify how close to that place they can get without being scared, then spend lots of time going to that place they’re not scared in - if that’s half-way up the wall then fine - on her go she gets to climb to the middle twice, she still does the same amount of climbing, but she’s not developing a habit of being scared or associating climbing with fear.
If she enjoys climbing, her curiosity and impatience will probably mean she chooses herself to go a little higher and you’ll see her start to grow the boundaries of her comfort zone. This can be facilitated by asking her to re-identify where exactly she gets scared, or even “would it be scary one hold higher? If you’re not sure let’s go up there and see what it would be like”
Sorry, rambled a bit there!
Hope something useful there for you!