Hello. I would really appreciate some help.

I'm trying to imagine a situation in the English language. Do you think my tenses are correct?
So, my friend calls me and says she can't come to the party. What would she say, "I won't come" or "I'm not coming" (I think it's the first one). And what would I say to the other guests, "She is not coming. I've just talked to her on the phone" or "She won't come" (I again think it's the first one).
Thank you for your great help.

Your tenses are correct in each of these. "I'm not coming" seems more polite than, "I won't come", but both are grammatically correct.