I don't hear a question here, but it is very uncommon (especially for a girl) and easy to see why it upsets people. I'm a guy that has a pretty insane schedule, so I know that I will forget important dates and make sure that I have calender reminders to make sure it isn't affecting people around me.
Honestly, it is just an excuse to blame something like adhd or whatever. You say that you don't forget things- except for things that are important to other people (birthdays, anniversaries, etc). Kind of selective, selfish memory lapses you have there!