I have the papillon 30 in mono and use to have the papillon 26 in both mono and damier and sold both 26s. I love the 30 size, it holds so much and yet does not look huge! If you are very petite with small arms, you should be able to wear it on your shoulder; however, it will not be a comfortable shoulder bag though, just want to pass that on to you. I love the Pap 30!
I'm a few inches taller than you and about the same weight and I really love my damier papillon 26. I tried them both on and the 26 just suited my frame better. I think (as I will always say) you need to try it on and see what works best for you.
The Papillon 30 is a handy size - not too small yet compact enough to carry around in style and comfort. I have trouble carrying it on my shoulder - it tends to squash up and look weird, but it looks great on the arm. The mini Papillon that accompanies it is ace. You can loop it on the outside of bags and use it as a mini bag on its own.