I'm going to show my 9 year old little sister pictures of measles victims in an attempt to convince my mom to vaccinate.
Why not show it to your mom instead?
Because my mom is stupid. Maybe if her baby daughter pleads the case, she'll relent.
It's possible that hearing an emotional plea from your sister will convince your mom. Showing graphic images to your sister though may frighten her so that might not be the best idea. Instead, have a discussion with you, your mom and your sister.
That's a good point. I'll take your advice!
I think you are making the right choice! If you can convince your mom to get your sister vaccinated, it would be great for your sister's health. Hopefully the discussion with your mom goes well!