police

If Tim knew the specifics of her story, if he had questions about what her husband had done, in all of their nights out and their meals together he’d never let on. They never talked about politics, and, while he’d asked her questions about Lizzie and Diana and their lives, he’d never once asked about Richard. Sylvie policed her own conversation carefully, and she didn’t think she’d ever said Richard’s name in front of Tim.
"police" となると直ぐに警察を連想しますが、上の引用個所に出てきた動詞の "police" は警察とはどう考えても無関係です。次の辞書に上の意味に近いと思われる説明がありました。
・Macmillan Dictionary: to check that organizations or people behave correctly; To limit or control something or someone:draw a line in the sand, limit, control...