Or maybe they are having an affair. And the husband in question refused to leave his wife for her. And this is a way for her to get him all to herself. Either way the situation is fishy, to say the least.
I still think you should talk to husband first. Feel him out. If he is cheating it is still better for her to hear it from him rather than you. I know your best friends but this is a situation that involves her and her husband. And she would probley rather hear it from him. But do investigate a little.
Don't just ignore the situation. Ignorance isn't always bliss. And your friend may be hurting already with suspitions.
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