Roni:
I'm going to say from a woman's point of view what has probably happened...
You said that she was Latino.
She most likely feels then that the man is the head of the household.
Even if she says/acts like that's not the case, it is probably ingrained somewhere down in her subconscious.
This being the case, she went along with it as long as you were the one doing the spanking.
Once you wanted her to do it, that changed the dynamics of the relationship...in a way she doesn't want to go, and was not aware of you wanting to go before she married you.
Since the possibility of the male (husband) occasionally taking the bottom role apparently wasn't discussed before the marriage, this explanation does seem to make sense.
The whole "machismo" image doesn't strike me as having any value or virtue in modern society, but it's still obviously a societal norm among many Hispanics...

--C.K.