Ron's choice of two words in particular stuck out to Hermione; get away. That was exactly why she hadn't stopped him taking it. "Does that make it better? My not knowing where you are, when you want to get away from me?" Because it wasn't as if she was about to join him wherever he had been drinking, and she didn't see the harm in at least knowing where he was and that he was okay.
He had confused her that morning when it came to what he wanted from her. He wanted her there, but he wanted to get away, she was supposed to treat him normally, even when the situation didn't require it, and then when she did he got annoyed with her... Hermione was having trouble understanding just exactly what it was she was required to do to get it right.
But her train of thought was interrupted by Ron advising her that he was back on regular duty when at work, and she finished his sentence for him. "So... I'll be needing it."