A Woman: That is neither an excuse nor mitigates her crime. Under the laws of England at the time, she committed a capital offense (as she was the consort of the Crown Prince of England) and was liable to be hung. (Incidentally, what she did would be chayiv misa under our laws too.)
Additionally, Charles was no worse a spouse when he got married than William is today. If I recall some stories of William of the last number of years, he may have an even more iniquitous reputation than his father had at the time of his marriage.