need advice on my friend and our teacher situation

ok so like i dont even know where to start but my friend has been like seeing one of our teachers… like actually dating or whatever? at first i thought she was joking but she keeps talking about him and going out of school to meet him. i tried telling her its super wrong, like its unprofessional and could get both of them in trouble but she just laughs it off or says she knows what shes doing.

i mean i get that people like people but this is our teacher… shes supposed to be a student and he’s like… in charge of us? i dont even know if he’s being responsible, like sometimes he’s acting really weird in class and i think maybe he’s doing things he shouldnt. i feel stuck because i dont want to ruin my friendship but at the same time this feels really off and kinda scary.

idk what to do, i cant just ignore it, and i dont think i should like tell other people but maybe i should? maybe theres some way to help her see its a bad idea without making her angry… has anyone been in a situation like this or know what i should do?