Don't allude, state. Say what you mean and mean what you say, or don't say anything at all. Dropping hints and alluding is just torturing her in my opinion. I'm not saying make promises you can't keep. I'm saying tell her the truth, whatever that truth is, and stop worrying about her feelings. There is enough lying because of the disease of alcoholism, enough passive-aggressive pseudo-communication, and enough enabling.
Not one of us here can promise we will never leave our spouses. Nobody can. What you can tell her is that if she does not find recovery you are certain to leave her and take your daughter with you. What you can tell her is that the only chance for your marriage to be saved is for her to find long term recovery. What you can tell her is the truth.
Take what you want and leave the rest.
Cyranoak