Can you imagine the guilt and shame she feels, weaving her tangled web of lies? Or, do you think she really just doesn't give a dam and does it to be spiteful? I truly believe some people are pathological liers (OMG, how do you spell lie-ers???), and they can't change the way they are. Once you can peg your x as this, it won't be so hurtful to you when she lies. You'll just chalk it up to the x being the x and move on.

Either way, I would refrain from trying to catch her in lies. It's probably unhealthy for you to be worrying so much about what she's doing, and who she's lying to. You can only control you. If she wants to be out of control, so be it. Let her dig her own bed and lie in it.

I personally believe in always telling the truth. However, if you know you're going to hurt someone in the process, then tell the truth in love so you're not being vindictive, or chastising them unnecessarily.