backpack or suitcase for 1 year traveling ?

[geecee]

Backpack definitely. Get one with as many pockets / storage areas as possible, some have hidden compartments. Try to get a backpack cover so that a) it is protected in the rain and b) when on the trains, buses etc, a visible pocket can be cut open, but if the whole thing is covered, it is not obvious where the pockets are.
Travel light - I would say bring four sets of clothes and buy cheap as she travels.

I desagree stronglky with the comment above about loads of pockets.
In my opinion the bag should have one (Or max 2) lockable compartments...Remember that the backback will quite ofte be out of your site (buses, taxis, porters, checkin etc etc) Its too easy for people to sneak drugs into your bag when there are so many places to hide things