"Nun, mir reicht es jedenfalls."
Maybe your translation does not have the right "being annoyed" connotation to it? Sometimes it is quite hard to think of the exact translation they want to hear.
That sounds neutral or positive to me. But the speaker is clearly annoyed about something.
I don't hear the speaker as annoyed, but jedenfalls isn't that more a matter of tone than words?
The expression "jemandem reicht etwas" has a negative connotation. there may be a neutral context but generally it is negative.
I'm sure you've forgotten all about this sentence by now (3 months later), but I understand "I've had enough" to be along the lines of "I've had it up to here with you" or "That's the last straw". As in my mother yelling "I've had enough of you two! Go play outside!"