Sizing - it is best measure her feet in cm and add 1 cm bigger. If it is 11 cm, then go with 12 cm
For soft sole measurement:
10.5 cm - 0/3 months
11.5 cm - 3/6 months
12.5 cm - 6/12 months
13.5 cm - 12/18 months
14.5 cm - 18/24 months
For hard rubber sole measurement:
11 cm - 0/6 months
12 cm - 6/12 months
13 cm - 12/18 months
14 cm - 18/24 months