Sounds like you're keeping good boundaries with her. I used to say my kids thought I was really stupid when they were teens until they were about 23, then all of a sudden mom was a genius again!
I was going to chime in with this very thing.
As tough as it is - and I know that it is indeed tough - it's pretty much completely normal. I went through this with both of my kids. A "lot" easier to do when there are 2 parents to double-team the kid. Part of what makes it tough is that she was / is such a sweet kid.
I had this up close and personal from my son, especially after he moved home, it was just the 2 of us and there was the extra stress of his mom and I splitting. It was as if he was holding me to a higher standard and not realizing that Dad is "just zis guy, you know". In hindsight undoubtedly part of the problem for me and perhaps for you is that the kid has the perception of options. My son spent pretty much zero time with his Mom but I'm sure things were all sunshine and puppies when he did see her.
As always this is one of those things that the only answer is time. Time for little G to realize that Mom is just a woman doing the best she can in difficult times. That the world doesn't revolve around her and that real life as opposed to the Disney life with her Dad that isn't the norm.
On BD H52, W50 T27, M26 S21, D23 BD-9-Mar-16 D-15-Jan-18 Final-19-Apr-18 I am a storyteller. The story may do you no good. But a story is never for the listener. It is always for the one who tells