All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
No doubt, what this woman is doing falls short of her duty to her husband and her children. So, anyone who knows her should advise her as it is an obligation on the Muslim to advise his Muslim brother in all matters of this life and the Hereafter.
Jareer Ibn ‘Abdullah narrated: “I have given a pledge of allegiance to the Prophet of Allah to testify that None has the right to be worshipped but Allah, and Muhammad is His Messenger, to offer prayers perfectly, to pay Zakaah, to listen to and obey (Allah's and His Prophet's Orders), and to give sincere advice to every Muslim.”
So, the Muslim should not interfere in his brother's affairs except by advising him to do the good he would want to be done to himself. For instance, if the Muslim sees his brother about to do something that could cause him harm in this life or the Hereafter, he should make clear to him and in a kind and wise manner the consequences that might result from his act. So, if his brother accepts the advice, then that is good, otherwise he will have done his duty. Another obligation of the Muslim to his brother is to advise him to enjoin what is good and forbid him from what is evil. The Prophet said: “The religion is advice.” They said, “For whom?” He replied, “For Allah, His Book, His Messenger, and for the leaders of the Muslims and their masses.” [Muslim]
Allah knows best.