Why oh why again am I having to manage poor 12yo dd1's utter anxiety over her Crap Dad's feelings around whether he will be attending another school concert, when he lives 1mile up the road and simply can't be arsed despite owning a computer and being fully aware of where she goes to school/how to find out what's actually happening in her life. I can see her really struggling with it, she has enough on her plate and so do I with working a demanding job and bringing the dc up singlehandedly
I think it's the 'veneer' he presents of being a good dad (which he puts on for the benefit of the new gf) which makes it all so confusing for a girl her age. I just want to scream out loud: HE'S AN UTTER ARSE to just let the truth ring out and end her confusion so we can all just get on with life.....
Honestly it would be easier if he'd gone under a bus.
Do you try to make excuses for him? EG "Oh maybe daddy has to work late" or "He's not very well"? I think we do try to shield our kids from how crap their parents are, it's a natural protective instinct, but I think it's actually better once they get into their tweens to just sit back and say "I don't know why he's like this" or just "You must feel very sad that she never phones you."
Of course it's very tempting to go for the full on "BECAUSE S/HE'S A NARCISSISTIC SELFISH LOON" but that is best saved for adulthood, IME.