"Act" is both a noun and a verb. In your example, you would use the verb, "She acts so rudely that nobody likes her." If you want to use the word "actions" you can say, "Her actions are so rude...." but it really doesn't sound like something a native speaker would say. You can use the word "behaviour" "act" as a noun usually refers to a part of a play (In Act 1 of the play, we meet the main characters) Another meaning is a law passed by a Congress or another governmental legislative body. An act of Congress. The Civil Rights Act. The Voting Rights Act.

No, act is not natural in this sentence, action works a bit better Her actions were so rude that now, nobody likes her Examples He was very friendly when we met but it was just an act That child always acts like an angel

Hi! "Her act is so rude that nobody likes her" *** You may rather say something like this: [She acts so rude that nobody likes her.] [She acts rudely that nobody likes her.] [She acts in a rude manner that nobody likes her.] [Her behaviour is very rude that nobody likes her.] Have fun!