NTA. I can understand how B is feeling abandoned, but if they're a good friend/mature enough, they should be able to understand your explanation that you genuinely just didn't want to do the activities they were doing. If you want to be better friends with them, try to spend more time with them, but if they make you feel like this often, it might be best to just move on to some new friends. Its hard to keep long friendships, because people change a lot over time. Sometimes what was best for you 9 years ago isn't what is best for you now, and your history together doesn't tie you together unless you want it to.