I know that she cheated and she continues to make up excuses

Answer 1

Mate, when you catch them out they 1, deny and lie, or 2, expose their claws like a cornered tiger.

Often, they will blame you to cover their guilt and have less s*x with you because they don't wish to cheat on their new "love". Women will always make up excuses for their behaviour, they couldn't lay straight in bed. Years back in 1979, I caught mine in bed with a male 35 years her senior (in his daughter's home) to this day she still denies it (I only took her back because of our then very young children) Good Luck - you will need it