Your sister is not getting married in order for you to get plastered. Wine is best consumed with food or around mealtimes. Education helps prevent alcohol abuse, and we're all responsible for conveying the lessons. Spend five minutes with a surly drunk and you'll get the idea. Parents should set an example of moderation.
Parents are the key educators in any child's life.
The choice to not drink, for whatever reason, must be respected. Being pushy is bad enough, but pushing alcohol is both rude and dangerous. Drink wine slowly, savor it, taste it, enjoy it. Remember you're enjoying the moment, not obliterating it. It's stuff we all already knew, but now is a perfect time for a reminder.