Luckily most people are going to be like your sister.
Sometimes people have their own shit going on that might make them “overreact” to your slip ups.
Weirdly you’ll see people that trust you more react more strongly but it’s not a you problem. They’re likely venting against constant micro aggressions in a “safer” space, so try and be forgiving:)
You’re right about it taking more work the longer you’ve known someone the harder it gets… It takes zero time for me to register “they/them” for someone I just met… But I still fuck up with a 20 year friend that switched 5 years ago…
Just remembering it’s not about you and as long as you try your best you’ll be fine.