I am sorry for your pain Jill, it's never easy, there are so many issues it is hard to be cut and dried.
I agree with Roo, there are so many people who lie for so many reasons, for me it would depend on the lie and their intent. Personally I am probably too forgiving, drives my hubby crazy.
Like Lara, I can see the grey so often, but many people can't and don't want to...and that is perfectly understandable. Each person has the right to set their own standards for their friends.
For me white lies, lies of convience and lies of exaggeration are part of human follies, and while I don't condone them, I do understand them and usually, easily forgive them. It is clear there is no intent to hurt others, often the intent is to save someone else's feelings, or made out of their own insecurities.
Lies that deal in fraud and manipulation, where the intent is clearly malicious, I do not forgive easily. My ex husband is my ex, because although I tried, I could not forgive his lies. These are people that are easy to dismiss from our lives and not give a second thought or glance to.
The hardest ones are the ones that fall in between. The lies that are made out of shame or self preservation. So many times it easy to see why the lie was made, but many times the under lying transgression is as bad as the lie. These are the hardest to decide forgive. Because usually you are dealing with a compound problem, the initial transgression and the lie. People make mistakes, people do lie to cover up their mistakes. How many times, do we see it...a bad situation made that much worse with lie.
I sure many of us parents would agree, this is something we try and instill in our children...'you are going to make mistakes, no doubt about it...but when you do, have the moral fiber and courage to admit it, fix, it if you can and ask for forgiveness, don't make it worse with a lie.' Human nature is to lie to protect yourself, that is why small children do it, they have to be taught it is wrong. It takes work, it takes vigilance, many people simple do not have the upbringing that has taught them that a lie always makes the situation worse. In fact, volunteering at the school, I see the opposite...parents actively lying for their children, making excuses for them, etc....do you think those people will ever hesitate to lie to cover themselves? Do we take that in account when we consider to forgive?
Like I said, for me, I tend to over forgive (just as I tend to over trust)...but each person has their own tolerances and it is perfectly acceptable to decide you can't forgive....and if you can't forgive, give up the friendship...afterall, is it really a friendship if you are seething inside?