=O Teach me your ways. Any way you can walk me through that?
Well do you only have LR3? Or do you have Photoshop as well? I can't walk you through every minute detail, but I listed the tools I used. You will have to learn to use each them and then the rest is just a matter of taste as to how strong or how weak you adjust them. As for cloning, just look up how to use the tool and then practice on spreading the darker part of her cheek just next to her mouth, across the rest of her face. I also added a little blur just to smooth out the cloned areas. The dodging and burning is just eyeballing it with a low exposure setting to slowly add changes ( although I am not extremely happy with how her skin tone came out, but given the small pic and the time I was prepared to waste on it, it was good enough and looked better in the B&W ) Hope this helps.
I would also heed kmh's advice, the best fix for this type of shot is to avoid shooting it, or when it does happen, cut your losses and re-shoot with better circumstances. Learn to use flash effectively or use reflectors and let the sun help you instead of working against you. Call it a lesson learned. However, I will just assume that this is a photo that you are not able to re-do.