The sizing of this top is relatively small.  The gathers at the neck and the batwing sleeve give it quite a lot of wearing ease around the bust.  It's hard to give a definitive bust measurement as the batwing sleeve is included in this.  I have measured where the arm meets the body, which is just below the bust.

I would say a size S/M is 8-10 and L/XL is 12-16.  Lucy and Arliah are both wearing the L/XL.

These are GARMENT MEASUREMENTS not body measurements.

S/M (8-10) L/XL (12-16)
At point where sleeve meets body. 100 cm 110vcm
Waist  100 cm 110 cm
Shoulder to hem 52 cm 54 cm