My wife's best friend (baptized catholic) is going out with a divorced catholic. There are talks that he will propose. I told the wife I wouldn't be able to go since it wouldn't  be a Catholic wedding. Even though I already rejected a friend of mine's wedding on the same basis now she is freaking out since it's her best friend. Our relationship is already on shaky ground so this issue can have the potential to cause a separation. In reading the following article I was wondering if the  following paragraph was true or a novus ordo invention.

"Canon law does not prohibit Catholics from attending invalid weddings, Father Pacwa explained, but he said that Catholics must discern carefully. “Every situation will call upon our reserves of prayer, discernment and evaluation,” he said. “And a good confession before making any decision is always a good idea.”

http://www.ncregister.com/daily-news/the-other-marriage-debate

Forget it's not a "Catholic wedding"...it's not a wedding at all; he's still married.  They're just going to shack up according to man's law.

Prior to Vat II we were prohibited from attending a valid protestant wedding because we were not allowed to worship with anyone outside the Catholic Church.

Your wife needs to decide who she wants to please, God or her best friend.  In this case human respect is the wrong choice.

If this is her "best friend" will she be asked to be Matron of Honour?  That would certainly be condoning their sin.

Sorry to hear this could be a deal breaker....I hope it's not.

As for Canon law I think they are talking about weddings performed where both parties are actually FREE to marry.

Sorry I clicked quote instead of modify

Theoretically, you could attend. One of the reasons that canonists give is grave civil duty.

You can't attend theoretically or any other way.  HE'S MARRIED unless he's gotten an annulment.
This does not fall under civil duty.  Social maybe.

Attendance would condone his sin thereby causing scandal.

Parents of divorced children have to make this decision all the time and it breaks their hearts.
This is just a friend.

OP, you might benefit from consulting McHugh and Callan (or any moralists you might own) to get a better handle on all the conditions required for lawful, passive attendance at some non-Catholic ceremony or another:

http://archive.org/stream/moraltheologyaco35354gut/35354.txt (esp. para 973 ff.)

My wife's best friend (baptized catholic) is going out with a divorced catholic. There are talks that he will propose. I told the wife I wouldn't be able to go since it wouldn't  be a Catholic wedding. Even though I already rejected a friend of mine's wedding on the same basis now she is freaking out since it's her best friend. Our relationship is already on shaky ground so this issue can have the potential to cause a separation. In reading the following article I was wondering if the  following paragraph was true or a novus ordo invention.

"Canon law does not prohibit Catholics from attending invalid weddings, Father Pacwa explained, but he said that Catholics must discern carefully. “Every situation will call upon our reserves of prayer, discernment and evaluation,” he said. “And a good confession before making any decision is always a good idea.”

http://www.ncregister.com/daily-news/the-other-marriage-debate

You can't attend their celebration of going to hell together. How's that for being direct? That is exactly what they are choosing if the abandon the faith and shack up together.

Now, as for your wife's best friend, she should have been advised from the beginning never to date men they could not marry.

I found out one day that a female relative was going to marry a divorced Catholic. I think the man had an annulment (ANYONE can get an annulment today). I immediately wrote her an "anonymous friend"  letter telling her many things, in brief, that it was a big mistake, that an annulment today meant nothing, that the person would leave her just as he left the other, that she deserved much better .... I sent the letter to a friend in another state and had him mail it in a new envelope. I did my job, and I prayed for her and and let God sort out the rest.
I found out like two months later that the wedding was off, that she had caught him cheating on her. God sorted it out.

As you can see, the important objective here has nothing to do with you attending the wedding, but both of you convincing the "best friend" to choose God rather than this unfaithful divorcee.

No one is lost without knowing it, and no one is deceived without wanting to be. (St. Teresa of Avila)

Sorry Mater but it sounds as if you're saying "go along to get along" both with the girlfriend and the husband with the wife.
If the husband gives in on this possible deal breaker to his marriage it could be worse than not going to the wedding as the wife will threaten the marriage whenever she wants her way in the future.

What happened to the catholic  stance that the man is the head of the family and has the final word regarding the faith?  This would turn the authority over to the wife.  Also the wife should be concerned about her own soul before trying to be an example to her friend.
As for Canon law I don't believe they are talking about a divorced situation.

Would you still interpret Canon law the same way if the wife's girlfriend was a lesbian marrying another woman?
The marriage would be invalid.
A sin is a sin and we can't condone it.

Sorry Mater but it sounds as if you're saying "go along to get along" both with the girlfriend and the husband with the wife.
If the husband gives in on this possible deal breaker to his marriage it could be worse than not going to the wedding as the wife will threaten the marriage whenever she wants her way in the future.

What happened to the catholic  stance that the man is the head of the family and has the final word regarding the faith?  This would turn the authority over to the wife.  Also the wife should be concerned about her own soul before trying to be an example to her friend.
As for Canon law I don't believe they are talking about a divorced situation.

Would you still interpret Canon law the same way if the wife's girlfriend was a lesbian marrying another woman?
The marriage would be invalid.
A sin is a sin and we can't condone it.

I, too, do not know if that part of Canon Law only applies to valid marriages or all non-Catholic services. It seems to me, though, that it would have spelled out "valid only" if that was an intended limitation.

I think at the time the Law was written, a marriage to a divorcee would have fallen under "scandalous".

I told the wife I wouldn't be able to go since it wouldn't  be a Catholic wedding. Even though I already rejected a friend of mine's wedding on the same basis now she is freaking out since it's her best friend. Our relationship is already on shaky ground so this issue can have the potential to cause a separation. 

If he is divorced then it is not a marriage at all, let alone a Catholic one. If his marriage was annulled it is a different matter. You make no mention of annulment. There is a difference between divorce and annulment. 
It is not good enough to say, as one poster has done, that anyone can get an annulment. There are some annulments which are justified and not all can be dismissed. 
If you really meant he is divorced then stick to your word. Don't go.