I haven't ridden the 2013 7'4 but I would imagine that it feels pretty similar to the 2013 7'7. I have both the 2013 7'7 and 2014 7'4 and once you get used to the new 7'4 I find that I haven't used the 7'7 much. 53Kg would be perfect weight for the 7'4. You would still have plenty literate. Just remember that it is a big jump from 8'5 to 7'4 (especially the 2014 one) so be prepared that she might need a few weeks to get used to it