Ssisters wedding in cancun. but why wont she care about the cartels and our safety?

My sisters wedding is in Cancun next year in may. However we live close to the border and see and hear about cartels enough as it is. N we aren't even in Mexico yet. Mom mom has tried to explain to her all the first hand experiences friends and family have had in Mexico. My sister refuses to change the location and snaps back at my mom with remarks about not even getting married anymore Because of my moms concerns. My mom has even stated she doesn't care for her life but my siblings lives and my own. My sister insists that her bf watches the media 4hrs a day and knows everything that is going on. However why wont they understand the media downplays the truth. My question is is my sister being selfish or are we for our safely. Thanks so much