Viola.....it did fill me with anger! This was many years ago, when the kids were younger....they are grown adults, now. It was hard.
One thing that did help, was when I fully accepted that he was going to be self-centered and irresponsible toward his children. He was simply not going to be the conscientious and nurturing parent that I had wanted him to be (for the sake of the children). I lowered the bar very, very low. The less I expected--the less I was disappointed. I detached from that man as much as humanly possible...given that we still had dependent children together.
I did try very hard to do what we are advised to do--not "talk bad" about their father around them or to them....but it was hard!! I practically ground my teeth to nubbins..lol....
When I saw the children disappointed--that was the hardest part....the only thing that I could do was allow them to freely express their disappointment...and let them know that I felt their pain and understood their feelings and that they were entitled to feel bad....
Like...instead of saying "your dad is a jerk" (he was)....I would say things, like---Oh, honey, I know you are disappointed or angry at him...I would feel the same way, If I were in the same situation.....and, hug them....
As they grew older...they began to be able to "read" him, themselves.....and, as adults, they will freely say that they know what he is like....
I agree with you...I wouldn't tell her that he was in town and didn't see her...she might find out--she might not. I don't see any need to point out things that will hurt her, even more.
As a young adult...she will have to learn to deal with him, on her own, without you as the buffer...and, she will...We can't shield them from the realities of life, forever.....life is full of disappointments, big and small, and we al have to learn (eventually) how to roll with the punches.....sigh.....
However...I wouldn't lie to her......
Your relationship with her, in the future will be better if she know that she can trust the things that you say.....
This isn't easy...it is hard!
Just try to not let it overtake you....try to re-channel the anger, the best as you can.....otherwise it will just eat at you, inside...and he will just be skipping, happily, down the lane.....