Stop Playing Games
I hate games. If you guys are really best friends, you really shouldn't be playing head games with each other.
Your Ridiculous Situation
She shouldn't be making up stories about boyfriends, and you shouldn't "be unavailable." This whole business with the coworkers calling you sounds ridiculous! Do you people ever talk WITH each other, not just AT each other?
Get Over Her
If you can't get her to express her feelings for you, there are two possible explanations:
- she doesn't have any, in which case it's time for you to get over her and find someone who does, or
- she is incapable of expressing her emotions, in which case it's time for you to bail and find someone who can.
I realize I'm being extreme, but it sounds like you needed a wakeup call. Lay it on the line with her, and if you don't get the response you're hoping for, take some time and space for yourself and move on. If you DO get the response you're hoping for, well... the rest is up to you! ;-)
Figure Out What's More Fun
Taking a best friendship to the next level is risky. I've done it and been happy, and done it and been burned. It's up to both of you to weigh the risks and figure out if the benefits are worthwhile. It can add a wonderful dimension of intimacy to your lives, or, if it doesn't work out, drive a wedge between you that will be hard to remove. The most important thing is to have fun with each other, as friends or whatever you are if you think you'll have more fun as friends, don't change.