ADHD and Travel

Hi Folks, Hoping you all can help. I've been together with my girlfriend for 6 years and it has been very rocky. I suspect she has ADHD and exhibits conflict seeking behavior and is never on time for anything. I have asked her to come to counseling with me, but when I tried to set it up, it didn't fit with her schedule. I gave her the counselors contact info and tried to get her to set it up 3 times and that was 5 months ago and still no progress. She refuses to even discuss the possibility that she has ADHD and gets angry when I bring up the topic. I would just move on at this point, but we have a beautiful 2 year old son that I love dearly. Even though it wasn't my choice to have children and I had told her so, she just decided to go off the pill and have a child. I see my son every night and weekend even though we don't live together since both of our houses are too small and I cannot convince her to buy a house with me large enough for all of us. To make matters worse, we haven't had sex since my son was born since I have a difficult time feeling close to her when she is so argumentative. We are leaving for vacation in 2 days and her Sister and kids will be meeting up with us. I told her tonight that I wanted to leave for the airport at 2:30 so that we are not rushed (we missed a flight on our last vacation because we were late) and that I was leaving at 2:45 with or without her. Of course she flew off the handle and told me that I didn't have to threaten her that she was an adult. I explained that I was not threatening her but that I wanted her to fully understand what my plan was and that I didn't need the stress. The question is, do I leave for the airport by myself when she is not on time, and let her get there herself and incur her wrath while on vacation or should I just leave and stay home and let her spend time with her family on vacation? I'm at my wits end and tired of rushing to the airport and would prefer a more harmonious relationship. Any advice is appreciated. Thanks.