Brian Walshe and his wife Ana fought just days before her death because she missed Christmas Eve and Christmas Day with her family to spend time with her lover ... this according to the lover himself. William Fastow took the stand in Massachusetts Thursday ... pulling back the curtain on his relationship with Ana ... with whom he says he was regularly intimate in the months leading up to her disappearance. Fastow says the two even spent Christmas Eve with his friends in Annapolis, Maryland ...