Is this considered an offense to classmates?

It's not offended.

If you have a very average relationship with this classmate, you better go and make it clear to her that you didn't wait for her reason. I suggest that you don't go with another classmate because you want to go with her, but be tactful and tell a little lie, for example, you forgot or something.

If you have a good relationship with this classmate, you don't need to explain it at all, and a true friendship will not be broken by a mistake.

It's okay, it's good to explain it clearly, but next time you have to learn a lesson, others won't tolerate you many times.

It's not offended, just explain it afterwards.

Of course not! Rest assured, there's a chance she'll blame you, but I'm sure she's just trying to get you complaining and not really angry. And didn't you also say that she wasn't stingy, so rest assured.

It shouldn't be offended, but it's better to find a time to explain it to her, so as not to make her feel unbalanced. Girls, think about something all day long.

You should say hello to her first and tell her that she can't go with her because she has something to do, and if she's a good friend and not stingy, then she won't think much about it. If the relationship is not very good, then you need to explain it to her. But this little thing won't affect the relationship between your classmates.

Take the initiative to apologize to her, and she will be fine.

Apologize to her and you'll be fine!

Just explain it to her, if she doesn't take it to heart. It's better to apologize.

If you have something, just say it, don't worry maybe it's okay to say it, the more worried you are, the more you don't say it, maybe it's going to be bad, but you also have to have your own principles for doing things!

I'm like this sometimes, I'm in a dilemma, I'm afraid of hurting my feelings, you think about how you feel from your standpoint, and he should forgive you if he's not stingy.

Don't count, sincerely apologize to her and explain.

No, just explain it directly.