Can you help? Well, by prayer, and really that is as far as it goes.
Honestly, you do not need to go there with her. Why? Because those details, that she may share with you could turn to gossip and well, that is not how to help her.
So, what are you to do? Pray for her, pray with her, and if she is wanting to talk to someone, find a pastor or outside person that is VERY trustworthy for her to talk to.
Most likely, if she is close enough to you to want to talk to you, you are too close to the situation. You know her, her husband, her children.
You can offer to watch her children, so she and her spouse can have a few hours to talk. But, do this tactfully. 
You can’t fix this, but, you can pray. Because God, is the one fix all we have this side of heaven.
Pray, pray and pray some more.
Getting involved with someone else’s marriage crisis is likely to create a crisis in your own. The best way to help, is to guide them to the proper help. Someone who is not as close to the situation, who is a Christian, who probably even maybe has a little training. I am not one to say counselors, but Pastors, or someone who has a known knack for this. For me, I am not that person.
Proverbs 27:14 NASB
He who blesses his friend with a loud voice early in the morning, It will be reckoned a curse to him.
To me, a loud voice could be considered advice, or counsel.
So, my suggestion, and what I have done, is to be there as a support, but I refuse to talk with the wife about the situation. I will pray with her, I will listen to her as she tells me she is upset, but I won’t discuss the situation.
My advice for my friends, is to talk with their pastor, or one who they are comfortable with.
