As you can see from the text Ava is a very hard working lady(.) right?
Well when people see that they see that she is becoming successful in life while they aren't. Teachers may not like her because she can be a teacher's pet too much, but the students are just hating on Ava because she's becoming successful plus she is a girl. When a girl gets to be boss or manager the other coworkers (men workers) get mad because they chose a woman over a man. Some teachers don't like her because she's just mabye failing or not asking questions, otherwise, they just want to hat her because she's just going too far in life.