Don't put the girl of your dreams on your buddy list.
Really. Don't. It will drive you nuts. Every time she comes online your heart will stop, hoping that she will drop you a message just to say "hi" or to ask how you are doing. It will crush you every time she doesn't bother.
It will cause you to create a separate screen name that she doesn't know, just so that you can check to see if she's online and be prepared before you really go online.
It will cause you to stop using IM software altogether because you risk talking to her in a less-than-ideal situation; for when you IM her, you don't get to see her run her fingers through her hair or look into your eyes and smile or do any one of the thousand things she does that make her her.
Don't do it until you know her decently well and can deal with it, even though it doesn't seem like a big deal.
Of course, that's just me, and this node proves that I'm a huge loser so YMMV ;)