Any suggestions what to do??

It's a very difficult thing to do and I've had to face the same problem myself with my gf(now wife).She came from a strict household where children were routinely spanked (not very rare in India even now)and was very scared of being spanked.The only way I see to solve this issue is to ensure that your Gf has complete faith in you and will trust you to any extent. Onyl then should you attempt to initiate a bdsm scene.I made this mistake of frocing her into it before she was ready for it and it took me some time to repair the damage. Even now, I'm slowly upping the ante,as it were,and am gradually increasing the intensity of the whole scene. I hope my experience helps you somewhat.