I know this is long but please read and help me.

I don't want to explain too much but I have a friend (who is under 18 and considered a minor where I live) who I think is being slowly pulled into a teacher student relationship.

Te teacher is married, has three kids and a partner. I'm too scared to tell u all specifics but trust me when I say the teacher (based on texts) doesn't give a sht they have a family. There is also some proof that my friend gets special treatment from this teacher who btw holds a powerful position in school staffing. They have each other personal contacts and message each other frequently and from the messages I've been shown; it's anything but school/mentor related.Recently, the teacher has begun to talk about their own love lives and has begun to address my friend (over text) with names such as "my darling" ect. My friend brushes off my concerns and yet actually seem to enjoy it.

What you u do? What should I do? Or should I do nothing?