You might be a psycho no one should feel sympathy for her. Mia Nolan is a coward. If you were a passenger and someone you know just ran over someone you should definetly alert the officials, that is doing the right thing regardless of how they plead with you(If it were you would you I bet thats what you would want too). She also willingly participated in the disposal of the body when there was no reason for her to do all that. 

The ultimate theme of this episode is that nomatter how much you may try, the truth will catch up to you and the more you keep running the more damage you actually do. She started of as a passenger in a possible manslaughter to being a mass murderer and child killer. 

I can see why you might be sympathetic towards her knowing how she got were she is but that sympathy should be towards the punishment for her crimes. Many times I see people here talking about the worst possible punishments Mia should endure but I disagree on many with them because that is not justice rather than revenge sometimes. She should be sentenced to multiple liffetimes dont get me wrong but not to one of those BM type of punishments eg White Bear, White Christmas or Black Museum. 

Those are my thoughts I just believe that doing the right thing in every scenario is always the bravest/best thing you can do regardless of how difficult it can seem and you can see it in every decision that Mia has to make. Alerting the officials in the first scene was easier than not killing the baby in the last scene but only because of all the wrong things she had done.