Woody - That must have been quite frightening. Kudos to you for making it out. I hope the OP isn't in as dire a situation but its good for her to know just how bad it can get.
@ Constructo Man - as had been said, counselling only works for couples where there is still mutual love and respect and a willingness to improve. My ex had to be dragged to counselling (he already knew everything they were going to tell him), with about the results you'd expect.
Sometimes, leaving IS really best for everyone. Particularly if there are no young children... why prolong the misery of 2 incompatible people?
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh