If there is ever any concern, you need to tell a trusted adult. You never know the extent of abuse, and even if you don’t think it is a major issue, it is still important to bring it up to someone. They do not need to directly confront the victim or the others.
Lei could overtime develop low self worth, worse bruises and marks, and could even develop mental illnesses. If there is a bigger issue, she could experience worse abuse and possibly even get to the point of death.