I read in the book called "The definitive book of body language" that this woman's instinct is an innate ability to decode a body language. When we lie there is always lack of congruence between body's microsignals and spoken words. Women catch this lack of congruence and it comes as a gut feeling. And if it's so, there is a possibility that someone can fake this congruence while lying. So your gut feeling isn't always trustworthy. But the final decision is up to you and there is no usiversal answer.

@Max thank you for sharing what you read Max.. In communication body language is important, especially eye contact, the absence of which will not help our instinct know the truth.. If for example a person prefers not to be seen, one cannot fell by his body language if he is being truthful or not. Yes, like what you said, some people can fake it.