She barely resembled the mediocre previous Penny. She barely resembled the mediocre previous Penny.

Or you could say "She hardly resembled the previous Penny."

The cast putascribed this astounding improvement down to her grief over her boyfriend and playwright’s death. The cast ascribed this astounding improvement to her grief over her boyfriend and playwright’s death.

The truth was that Penny was wrestling with the knowledge that her new lover, Bobby Melma, mightcould’ve prevented her boyfriend’s violent death. The truth was that Penny was wrestling with the knowledge that her new lover, Bobby Melma, could’ve prevented her boyfriend’s violent death.

It was a nagging doubt that had pushed her ton the verge of a breakdown. It was a nagging doubt that had pushed her to the verge of a breakdown.

Yet, her performance didn’t give anything away. Yet, her performance didn’t give anything away.

While Penny was at the theatre, Bobby was getting ready to start his own show at the hippodrome. While Penny was at the theatre, Bobby was getting ready to start his own show at the hippodrome.

While Penny was at the theatre, Bobby was getting ready tofor his own show at the hippodrome. While Penny was at the theatre, Bobby was getting ready for his own show at the hippodrome.

He too was inwardlywas also anxious. He was also anxious.

anxious is already an inward emotion, so it sounds weird to say "inwardly anxious".

He too was inwardly anxious. He too was anxious.

A better word to use is "self conscious" rather than "inwardly anxious"

Because ofMotivated by this fear, he had already disposed of every item he had stolen during his last break-ins. Motivated by this fear, he had already disposed of every item he had stolen during his last break-ins.

Stylistic change.

Because of this fear, he had already disposed of every item he had stolen during his last break-ins. Because of this fear, he had already disposed of every item he had stolen during his last break-ins.

You could also use "Because of his fear..."

Still, it hadn’t and wouldn’t ease his mind. Still, it hadn’t and wouldn’t ease his mind.

What does "it" refer to here? Unclear.

Still, ithey hadn’t and wouldn’t ease his mind. Still, they hadn’t and wouldn’t ease his mind.

they- in reference to "the police"

He would be haunted forever by the memory of the crime scene. He would be haunted forever by the memory of the crime scene.

Another stylistic spin could be: He would forever be haunted by the memory of the crime scene. You could also drop the word crime since the reader already understands a crime has happened.