Around 5-6 months I think, she might be a little slower though being prem, Kynon was born at 36 + 0 although i think he was nearer 35 weeks by my dates, and I've noticed he's a little slower with some stuff too, think it takes them a while to catch up even if they are just a few weeks prem. If your HV doesn't think there is a problem then try not to worry, I sometimes forget Kynon should be at the 12 week development stage and not 16 week!