In the play, Portia is the wife of Brutus and is known for her intelligence, wit, and strength of character. It is not explicitly stated in the play how Portia feels after Brutus leaves his house to go to the Senate house. However, we can infer that she may be worried or concerned about Brutus, as he is involved in the conspiracy to assassinate Caesar and is likely aware of the danger and potential consequences of his actions. Portia may also be feeling anxious or fearful about the future, as the political situation in Rome is unstable and uncertain.
Overall, it is likely that Portia's state of mind is complex and multifaceted, as she is a deeply perceptive and sensitive character who is deeply invested in the well-being of her husband and the future of Rome.