It's best to be friendly at a wedding and to talk to and introduce yourself to all the guests. It doesn't matter what order you do them in. Just do it in the order that you come face to face with people.
There's nothing wrong in asking really obvious questions when introducing yourself at a wedding, such as "Hi, I'm an8581096. I'm the groom's cousin on his dad's side... So, how do you know the bride or groom?... Where did you have to travel from to get here?..."
It's one of those times where it doesn't matter much how you chat and introduce yourself to everyone. It's more important that you actually do so.
And, of course one of the people that you will talk to at some point will be this attactive young woman.
There's a high chance that there will be other attractive available women there. Talk to them as well.