There a difference between the experience of 100 dives and the same experience on 100 divess.
You are always your own best buddy. I absolutely refuse to place my safety in the hands of another. Especially someone I just met. Be prepared to take care of yourself. Never count on your buddy for anything.
It's difficult to be the buddy of a photographer. I know because photography was my main interest in diving. Fortunately, my buddy was also a photographer. So, we were both solo diving together. It worked just fine because we were both capable of taking care of ourselves. We were usually within 20 or 30 feet of each other but, of necessity, our attention was on the subject, not our buddy.
When you're on a charter boat, you don't get to choose your insta-buddy. You might get to choose from a set of buddies but, in the end, you dive with someone you don't know. It sucks!
I was the 'new guy' in our little dive club and whenever I showed up without my buddy, I got assigned the tourists. A diver that didn't believe in dive tables, a diver with an undisclosed sinus problem, things like that. I have NEVER had an insta-buddy dive go well. That's the problem with diving with the same person for 100+ dives. You get comfortable. You enjoy diving.
So, suck it up! You got assigned a diver you didn't want. Well, that's just the way it goes. They are your buddy, you need to stick with them until they are back on the boat. No matter what! Then you can choose another buddy or choose to skip the following dives.
But once you hit the water with a buddy, they are your buddy no matter what!
Richard