I spent a good hour last night trying to kill her, with no luck.
Today, I just completely wrecked her.
The /only/ thing I think I did differently was instead of staying hear the hole during phase 2, I stayed way away, Beth didn't heal, and didn't cast widow's kiss on me, just melee'd my pet like a derp.
YOU CAN SOLO BETH TOO!
Requirements for a BM hunter:
At least 430k HP (I did it with 467k, crystal of insanity and scroll of fortitude to bring my stamina up)
A spirit beast, with Spirit Mend macroed for convient use
At least 70k DPS
Glyph of Mend Pet, Glyph of Animal Bond, Glyph of Misdirect, Misdired macroed onto arcane shot
Pet in Tenacity spec
When the fight starts, kill a spinner and go up the web, using deterrence before you reach the top; spam your pet attack button on Beth (your pet will usually come up with you) and then FD so Beth is attacking your pet. Then pewpew, staying AWAY from the hole (can't tell you how many times I fell down and got decimated by the accumulated spinners), and staying out of the fire circles she makes. When she casts Devistation, she'll bring you down to about 20k HP, which is when you should use spirit mend, and use it on cooldown until your health is at max. Other than this, the first phase is pretty easy.
For the second phase, she'll climb down, and your pet will follow. It is VERY VERY VERY important that you STAY FAR AWAY from the hole, otherwise Beth will be able to pull you down, where you will get devoured by spiders. Once they get down there, beth will either heal up by eating stuff, or not, seems to be a bit RNGy depending on if your pet gets aggro quick enough when she goes down, I'm not sure. Either way, just spam Kill Command. She will only melee your pet, and spirit bond will heal for more than she can hurt, spinners seem to ignore pets and can't hurt you when you're above. Eventually, Beth will die.
The end :D
