zen, why don't you just say no?

sometimes ppl with OCD can engage in very black/white thinking, and so it can be difficult to pick up on subtleties. but this aint necessarily an OCD thing - i know many ppl without OCD who become very singularly minded and ignore/don't hear subtle resistance.

if your friend didn't have OCD would you speak up? or would you find another trait to blame? i agree that she is being difficult, but i also think you have a lot of power in this situation and you aren't utilising it.