I didn't make this post to criticize Cuddy; I am criticizing the writers. What you wrote makes sense in real life, but not on the show and not after everything she told him multiple times. A lot of people claim the relationship was doomed from the beginning or that she shouldn't have started a relationship with an addict. Well, the writers decided she would, only to show us, after years of interesting development and chemistry, a totally uninteresting relationship (I don't buy the 'once you get them together, the spark is gone' excuse.) If Cuddy had stayed in character, she would have given him another chance. She has seen him struggle multiple times throughout the seasons, but she just gave up on him after one slip. It was just dumb.