Translation:Have you seen a picture of her as a child?
Let's replace "she/her" with "he/him"
A picture of him.
A picture of his.
Is this the same? I think it's not (might be wrong, English is not my mother tongue)
So "li/lin" is ENG: "he/him", and "lia/lian..." is ENG: "his".
"Ŝi/ŝin" is ENG: "she/her", and "ŝia/ŝian..." is ENG: "her/hers"
I hope this clarifies it a bit.
Please noticed "her" belongs to both Esperanto groups. Esperanto used capitalized "HER" below, not the one in small letters.
"Ŝi/ŝin" is ENG: "she/HER" - and "ŝia/ŝian..." is ENG: "her/hers"
Once again ENG: "her" is equal EO: "ŝi". I urge you once more to use the male pronouns which are less confusing in this matter, so the Duo's sentence would be:
EO: Ĉu vi vidis bildon de li kiel infano?
ENG: Have you seen a picture of him as a child?
Similarly: Ĉu vi vidis bildon de mi kiel infano? ...picture of ME...
That's all folks, I'm done with this advice of mine! ;-)