Thanks all for your info. I guess 160 iso for this film is fine. And yes, she in shade so she should be dark. The main error here is how i composed the shot with not enough difference in tone between my subject and the background. Exposing for longer would not change this relationship. So yet portrait falls down on not having enough light on the subject. I now have two reflectors, which will be an option for next time and i have a leaf shutter lens on the way so maybe a softbox also!
Thanks again all for the insights. am not sure i would have cracked it on my own.