“Happy with”,“Happy about”an “happy for” are all correct depending on the context.
We use “happy with” when you are satisfied with a current situation.
Are you happy with your current salary?
I am happy with how things are.
We use “happy about” more when in situations that involve actions that happened especially when we are not happy or weren’t involved in.
I see Donna is going on a date with James.
Yeah, I am not happy about it.
Notice that we use” with” more when the object is mentioned and we use “about” more with words like “it” and “that”.
The reality is that most people use these words interchangeably and there is no real difference in meaning.
The only difference is that we tend to use “happy with” when the object of the happiness is mentioned and “happy about” when it isn’t.
What about “happy for”
We use “happy for” when we want to show that we are happy for another person’s success.
I passed my driving exam.
Oh, that is so great, I am happy for you.
“Happy for” is nearly always used when the direct object is a person or people and is often used with a direct object pronoun(me, you, him, her us, them).