When me and my wife were on a packed commuter train last month I used the crowd as an excuse to push her ass onto a guys hand and hold here there for the journey. As the train made her move he felt up and down her ass and even once or twice I saw his finger between her legs.
She didn’t say anything to me as she’s shy and would have been afraid I’d get mad and make a scene. Instead she froze and I pretended not to notice.