All of these are reasonable. So I'm being picky here, just to offer more detail
Adding "not" onto "to xxx" verbs is alway tricky. In theory the rule is "never split infinitives", that is, never put a word between "to" and "xxx".
But it hurts our logic bump. "it is rude to xxx" we understand, "it is rude not to xxx" is confusing. How can I be rude by NOT doing something? How long do I have to continue not doing anything before it suddenly becomes rude?
Changing to using "greeting" instead of "to greet" makes things easy. "not greeting me was very rude" is good.
Or make the verb a positive one like "avoid". Then "rude to" works. "It was very rude to avoid greeting me." or "It was very rude to snub me."