Sorry, but I am personally against the whole concept of non binary and I was taught that they/them is plural, not singular, so I politely refuse to call anyone by those terms. See, this is why I don't like non binary people and people who support it, you see I don't like it, so you automatically don't like me and label me as rude and disrespectful. I have a friend who is the same, but she's okay with me calling her she cause she knows I don't like it, she's respectful, unlike you guys.
I feel sad for your friend. You really ought to respect their pronouns if they’re really someone you care about. They may say they aren’t bothered. And maybe they aren’t. I don’t know them. But the fact is that many ARE bothered. And if your friend is one, they likely don’t feel comfortable enough to tell you.