Q:

What does it mean? A record deal? And hating on somebody?

Some people started hating on my friend when she got a record deal. 
A record deal? what kind of a deal is it? 
Does the word "hating" mean envious? 

A:

In this context, a record deal could mean one of two things:
It could refer to a recording contract, where a performing artist signs a contract with a record label, also known as a recording studio. For example:

Beyonce signed a new record deal with Arista. Her new album will be released next year.

Or, it could refer to a deal that sets a new record (for something like salary) in any industry; for example, it would make your friend the highest-paid athlete in the history of her sport. 

Rousey signed a record deal that will pay her 40 million dollars over the next five years.

There is no way to tell which your sentence means without surrounding context, which is why we often exhort users to provide context when they ask questions here on ELL. 
And, yes, I would guess the word "hating" here refers to being envious. 

