Although Mary tried to get rid of Betty a number of times either by pleading with William and trying to have her detained in England, William only left Betty after Marys death.  She later married and had children almost straight away although I dont think she was ever recorded as having any with William.

We can only presume that William was happy with his lot with mary, well happy enough not to divorce Mary.  He loved her and she grew to love him, as he admitted he could have doen a lot worse, he was supposed to have remarked that if he had married Anne, he wouldve been the "most unhappy man in the world".  What if he had divorced her as her miscarriage meant hs eoculd have no more children, but then his new wife didnt give him any either?  That would have got embarrasing for him.  Maybe he  thought the problem was with him too, maybe he didnt, but what is clear though, even if he did marry Mary for her crown, he grew to love her and having a mistress was very common-it didnt mean he thought less of Mary just because he refused to give up Betty. 

Apparently, when she talked, she squinted more than people deemed necessary!