Wolfman moving forward 3

[Wolfman]

I need help with a convo ASAP. With the therapist yesterday my gf brought up a situation from April she was upset about. Try to make it short and to the point. Back in April I had a week off and I got my son for the whole week. So, about a week before I got him I said I wanted to take my son to Great Adventure of of those 7 days I had him. I told her I was thinking Monday. She out right told me NO.( 2 reasons I was taking him, 1. It was her idea if he got a certain number of 100’s on tests I should take him. 2. That week I had him I knew the park was not going to be so crowded.)
I said I can’t take him one day? She said no she had school work to do. I said I understand, that she has work to do, it was just going to be one day and the rest of the week I would help her by babysitting the baby. Which I didn’t think was fair for me and my son, that I was going to babysit and barely spend time with him. Make a long story short, I still took him on Monday. She was very mad that I took him after she told me no. Oh and as far as her school work, she finished it 2 days later and the assignment wasn’t due for another week anyway.
So she brought that up how she felt like I didn’t care about her school work and the things she needs to do. That I should have not gone, that I could have taken him in the summer. She was upset about that. The therapist asked me about my side of the story and how I felt. I explained what I said above and said I don’t think it would have been fair for my son to just sit in my house everyday while I babysat the baby. And basically only spend time with him after the baby goes to bed at 7 pm. How is that going to make him feel. And I had told him a couple of weeks before that I was going to take him during that break. When I said all of this, she got even more upset because when this all happened she kept at with me how I was wrong, I shouldn’t have done that. So back at the time I tried to validate and say, I understand why you would be upset, I am sorry you felt like I let you down. So she told the therapist I went back on my apology now. Feels like my apology was not real. Honestly I tried to validate her feelings back then and I did t want to continue to argue, considering she finished the project 2 days later, one week ahead of schedule.
She just text me she is still upset about our conversation from yesterday. This is what she just text me,
I am still upset about our conversation yesterday. You basically told me that my things aren’t as important as yours. Please help. How do I validate this? I don’t want to argue.