The situation was emotionally charged enough that Susan had expected a reaction to her words. She'd only said it in the first place to help absolve Charlie of any guilt for not having told his mother about his son. Still, despite all of the discussions she and Charlie had had in the past about their mother's respective fiery tempers, she hadn't expected quite Mrs. Weasley's level of anger. She turned her face away to hide the fresh tears welling there, but she didn't step away.
She wasn't ashamed. She regretted how things had gone, wished that she'd told Charlie sooner than she had, but she'd done the best she could under the circumstances. She'd done what she could to make sure that her son would have the best life possible, with or without his father's involvement, and she refused to apologise for that part, at least.
Susan looked up again when Charlie came immediately to her defence, both a little surprised at his corresponding vehemence and at the words. They'd talked around his leaving, but it was the most he'd said all together about it. It warmed her enough that she was able to look at Mrs. Weasley again, and what she found there was something familiar.
She was just a mother, wanting the best for her son, and willing to fight for it.
"It's all right, Charlie," she said softly, though her eyes stayed on his mum. "We both did what we thought was best at the time." After a pause, she finally stepped closer to them again, looking up at Charlie. She was too emotionally drained to really express how it felt to have him there and saying these things, but she hoped he could see at least a little of it in her face.
Then she shifted Nicky in her arms to transfer him over to Mrs. Weasley—to his grandmother.