Parent contacting dd directly is unreasonable

[Alter]

AIBU to be furious that a mother of a girl in my 14 yr old dd's year has texted her about an argument that happened between the girls. My dd has not been directly involved in the nastiness and supports this friend. Dd is a peacemaker, other girls have been nasty to her daughter and she has been firing questions at and directing her anger at my daughter. I don't know this mother personally, just the daughter, but her texts are quite aggressive. My daughter's text response has been very mature, reasonable and supportive to the friend but not a thank you. I think it's out of order for her not to speak to me directly, or even better, the perpetrators.

Yes I’d be really annoyed too. I’d be inclined to ask the mother to stop

Yes. I’d phone her up. She’s out of order.

It's a shame that your DD has responded. I would have advised not to reply and to block the number. YANBU.

This is really not ok. Get DD to screenshot the message then block both the Mother and the Daughter.

Talk to head of year and get school to deal with it (and to tell the mother not to contact another pupil directly).