Can i give you an example from my experience? my ex had a best friend. He had a fase where he talked to her more than he did to me. I was jealous. I wanted all of his attention (or at least i wanted more than he gave her)
at some point she started really poking at me. saying stuff to try and make me jealous or sabotage the relationship or something. She didn't succeed but that made me hate her.
Hate is when that person has done something to make you strongly not like them. They've done something to you that is unforgivable, you've heard nothing but bad things about them, they're evil, etc.
Jealousy is when you want something that someone has. For girls it's like this: Let's say a hot girl with big boobs walks by your girlfriend. Your girlfriend sees this other girl and notices she has bigger boobs than her. She says "her boobs are way to big" or "her nose is obviously fake" or something like that. She wishes her boobs were as big as that girl's, and wants you to not think she's hotter than that girl, so she makes a rude comment. Another example of jealousy is you hear that that a man just retired at the age of 25 because he made a billion dollars and now doesn't have to work the rest of his life. You've always wished you'd never have to work so when you hear about this man, you think "I wish I was him!"
Jealousy is just something you feel when you want something but can't have it or want something that someone else has. Hate... well... hate is an emotion of large dislike you feel for a person or thing.
When you are jealous of someone, you are 'defensive'. You don't want to cause harm to that person, you just want to protect your possessions. You don't want that person to take away your luxuries or do something better than you. But it doesn't mean that you don't want that person to have anything at all. As long as you are protected, in control, in better position than that person, you are cool with it.
But when you hate someone, you're 'offensive'. You want to cause harm to that person regardless of the context. You can't stand that person. You will try to obliterate that person or at least dream about his/her self destruction. You want enslave that person, make him/her helpless or change his/her values and mindset for good.