Thank you for your replay,
now she is in a box 40x30 cm the final one will be 90x50 cm.. should i move her when she'll be half way? (in this box she'll be fine at 70cm, in the next one at 140cm... if i move her when she'll be 105cm is it ok? or should i move before or later?)
A boy at a reptiles fair told me that concrete (cement?) is too rough and can hurt and it's really difficult to clean it if she poo over it, is it true? Are there other drawback on this kind of decorations? (i'd like to buy a terrarium with a 3D background made with concrete)