Oliver would become a liability if she took him with her when she ran. The first opportunity he had, he would give away their location. His father hung the moon and the stars in his eyes. Though she assumed there was love there for his mother too, she knew that he would do anything to get back to his father. When it was obvious that she couldn't take her child away, Hermione gave up her plan to run. The Muggle money remained where it was. Her other supplies stayed packed up. She would just have to endure what her life had become for the foreseeable future.