Guess what Mom. I don't drink any more.
[or]
Guess what Mom. I'm doing a Dry January.
[or]
I'm gonna pass on the wine. I'm trying to lose a few pounds.
I'm new here, Sohard, but may I ask how old you are? Not that it matters, but I'm just wondering whether your mother is a older person, set in her stubborn ways, or what.
But I say "not that it matters," because however old you are, or she is, you are the one who knows what best for you.
Do you agree with that? Then please do what is best for you. And you know what that is.