Freddorika "I'm a bit sick of it. I think the reason dd is overreacting is because she's also totally sick of it and on edge all the time. Shes much less cheerful generally which is sad"
This is very sad. Please help her work through how she feels.Why does she feel the need to please people?
Can you get her to articulate things to you and work together on what she can say to this boy. " that may be your opinion but it is not right." Not as harsh as piss off,which I may be temped to say, but still assertive.
"I would love her to tell him to do one. She won't though. She is definitely a perfectionist and a people pleaser." So you may need to help her articulate what she will say.
if she is a perfectionist can you work on showing her how things that are not perfect can be perfectly nice! A wonky pie that tastes good, an odd shaped flower that looks lovely and smells lovely too? Find things to show her it is OK not to be perfect.
There are lots of helpful tips on line. You can google around and find places to start.
blogs.psychcentral.com/imperfect/2016/11/overcoming-people-pleasing-perfectionism/
"Strengthen your sense of self
People pleasing and perfectionism are like shields that hide and protect your true self. The more pleasing and perfecting you do, the more out of touch with yourself you become; you no longer know what you like, what you believe, what’s important to you, or even who you are because so much of your time and effort is spent trying to be what others want you to be or an idealized version of yourself.
“Finding yourself” can feel like a big endeavor (and it may be), but you don’t have to do it all at once. Bit by bit begin to explore and experiment, constantly checking back in with yourself to see how it feels. Self-discovery truly is a life-long process because we are all constantly changing.
Learn to give yourself approval
You can’t allow your self-worth to be completely dependent on other people’s approval. One of the biggest shifts that you can make is toward increasing your own positive self-talk and self-compassion. By beginning to give yourself more love and acceptance, you can become less dependent on other people for making you feel good and worthy."
Work on this together, mum and daughter, and focus on HER rather than this boy. The things she learns from you now will stand her in good stead for the future.
Help her to build herself up rather than tearing him down. Remind her that he too is insecure, (crying about a comment). Maybe she needs to ask him directly "Why are you mean to me when I do well?"
She can remind him "We are friends, we can both do well and support each other."
She can warn him, "If you keep acting like this when I do well, you jus might spoil our friendship."