Ok, I need to think some more, but
A good mum is true to her word,if she says you can do/have something/go somewhere, then it happens, even if the child forgets, and if mum says if you do that again then x happens, then x happens. That means she is someone you can always rely on, someone dependable, someone who's word you trust.
A good mum will always be ready for a cuddle, and will be there, will just 'be' in the house, or somewhere near.
A good mum is a good role model, do as I do, rather than do as I say.
A good mum says sorry sometimes, when she has got it wrong and been too harsh
A good mum gives her child opportunities for friendships, for a support network that lasts years. I hope my girls feel they can turn to some of MY friends to talk to, when they are pissed off with me, or their dad, or friends, or whatever. I hope my girls have honest, good friends of their own.
A good mum lets their child be themselves, show their own personalities, gives them a chance to workout things themselves, to grow in confidence in the realisation that they did it.
A good mum gives their child time and opportunities to learn, to have fun, to reflect, to be bored, to be part of a family (however extended) and her child knows that they are deeply loved even in the shouty moments.
A good mum sometimes says no.
A good mum gives herself a break, moves on from the inevitable bad moments and learns from them, has her own sense of purpose, her own interests/work/hobby that gives herself self belief and confidence.
I think everyone will think something different, would remove lots from my list and replace with their own. mine has been fuelled by thinking while. ironing for two hours on a Friday night 