Occasionally he would beat her, but she just swallowed it with a sense of helplessness.

swallowed 是动词 swallow 的过去式，原意是"吞咽"，在这里用作比喻，表示"默默忍受"或"咽下（委屈）"。这种用法形象地描述了将不满或痛苦像吞咽食物一样压抑在心里的状态。