Drama question ewww.?

Theres these 2 girls at school. One of them is my friend. Another used to be. Im naming the girl whos my friend Dana and the other lily. Lily hates dana. She texts Dana really really rude things. Danas mom saw and told dana if she dosent tell a adult at school, her moms gunna do it. Dana doesnt know weather or not to tell because she doesnt want "Lily" to start more things. what should she do!?