I know a lady that her husband continues to commit adultery. She has told him that as long as she can forgive him that God will be able to forgive him also. I know God will forgive him if he wants forgiveness but if he continues in this same manner isn't she also committing sin by allowing him to do this. He has asked for a divorce from her but she has told him no because it is not in Gods will. Please find some bible verses that would shed some light in this situation.
It is difficult to find Bible passages that relate directly to this situation. The obvious ones are Matthew 5:32 and Matthew 19:9. Both passages say that a divorce may be allowable in cases involving fornications (possibly meaning adultery). She is right, to a degree, in saying that divorce is not God's will, but in this case the marriage contract has already been broken and the party at fault is obviously not making any attempt to fix it. She should prayerfully consider whether or not to grant the divorce, but either way he is likely to continue his ways as the situation now is.
She can forgive him, but is only hurting herself by doing so. Unless he asks her to forgive him she is under no obligation to do so. God will forgive him if he asks for it; until then God will not forgive.
I wouldn't say she was sinning by allowing him to continue his lifestyle. That is something she probably has little control over. There is not much she can do to prevent it, so she is not at fault. She would only bear sin in the matter if she were encouraging his actions or providing the other women for him.