How Kristen feels is not a matter of 'Should' or 'Should not', to make that judgement implies a knowledge of the moral code to which she adheres.

Your moral standards may dictate that she should feel shame for her actions, or they may say that each person must take full responsibility for their own actions (in which case Rupert Sanders takes responsibilty for his). In either case these are your moral standards not hers.

Human relations are complex beyond measure, to judge a person on one action or aspect of their lives ignores the complex reasons behind their actions and beliefs.

Theres is an assumed commonality to our existence, we think that each person should act in a way that we find right, and they normally do, as we live in a society that requires us to behave in a certain way to continue its existence.

When people step outside these boundaries it causes a bit of a fuss and gets the headlines (such as in this case). It can also cause us to question our own standards, actions and moral code, 'What would I do in that situation?'.

Let's not be too quick too judge her, I imagine that Kristen is judging herself more harshly than we ever will.