Whooping Cough and MIL issues.

So I asked everyone to get the TDap. My MIL blew me off the first time. I kindly reminded her again yesterday. She immediately popped off and said "its taken care of!"  I know she is lying. So I told her my husbands sisters and her husband need to get it. She said "stop worrying about it. We are up to date."  I JUST KNOW SHE IS LYING. so I stopped talking to her. She has been texting me all day and telling not to worry about them. What do I do! I meant I can't PROVE they didn't get the vaccine. Help!!!! Advise!!! What would you do!!!