Sounds to me like you are dealing with a poise problem. Even a light little thing can cause your wrist and arm (not to mention back ) to hurt if they are attempting to arch so far back that they are no longer in control of their weight.
First concider a few things. When you do a spin turn are you trying to keep her from falling away from you? One way to tell this is; are you losing body contact..... second , on the heel turn, is she trying to acually turn on her heels? If her weight is in her heels, she is definatly falling, and you will have to compensate by holding her up. thrid.. is she sustaining her rise untill the entire turn is done? sometimes ladies lower before the turn is done. Sometimes they just don't know any better, usually its a lack of ankel strenth, and almost always, bad poise.
A few thing to try that might help you out. Probably the most important, and most benificial piece of advise......... stand up!!!! If your lady is trying to maintain some kinda line by arching her back in some kind of rediculous angle to gain that "look", she is probably robbing you of lot's of mobility. Many ladys become sevearly back weighted by trying to maintain an "open top line". It is much better for her and especially her partner if she stands up straight and only "looks out". Something else, many people including a few coaches belive that contact is maintained at the hips. This is not really true. The contact point is higher, at the diaphragm. Here you should always feel a slight amount of pressure foward INTO you. Not back AWAY from you.
Poise is the feeling that you are ballanced and ready to move in any direction, without a well ballanced couple, the man will always feel like he has to " muscle " his partner, which is ALWAYS bad. Alex flexi@subdimension.com