Do you think that my neighbour was really rude?

I think that is extremely rude. You're taking your time to help with someone elses homework when you don't even have to. & you didn't get paid to do it. What you're doing is very generous & kind. I appreciate people like you. & if that person was late.. Well they were late & you have your own schedule. They shouldn't be upset at you. They should be upset with themselves for missing out.