When to let go?

Question : When is it time to let go? 

Here is a real life story...

*Serena been with her husband since secondary school. They have a daughter and she is currently pregnant again. However, the problem is her husband's infidelity. But she loves him too much to leave him. She met the third party and had a drink with the third party to have an adult conversation. There was no hair-pulling, face slapping, pour-water-on-each-other heated argument nor disagreement. The third party agreed to leave and not destroy her marriage.

Few weeks later, Serena saw her husband with the girl again. She has no choice but to separate them. But her efforts seem meaningless because no matter what she does, they always went back to each other. Even after she confronted her husband, her husband admitted he loved the girl and he wanted to keep both. 

Every time Serena's husband goes out, Serena would go out too. Her pre-schooled daughter followed her everywhere she goes and barely has any sleep. This has been going on for about 2 years. And now, she is pregnant AGAIN. Her last resort was to send his husband back to his hometown but she has some business to take care in her hometown.

*Not her real name.

IMHO : Serena MUST let go NOW.

Why?

Because she has fought for more than 2 years for that jerk. She did EVERYTHING she can to protect, to maintain, to restore her marriage. But her husband has yet to wake up from his "slumber", thinking the girl really loves him. She even have a 2nd child with him after he betrayed her. And as I said before, it takes TWO to work out a relationship, NOT one person alone or three. Now that Serena has TWO children to consider, more accurately, their FUTURE to consider. I'm sure they are not able to concentrate in their studies if they have to constantly move about and stay awake til wee hours in the morning or having to stay in Serena's friend's home. They are still young, Serena IS still young. What is there to lose if she leaves him? She has the ability to support her children AND herself. But if she don't leave him, not only she ruins her life, but also her children.

But she has been dating him for so many years, spend so much time in this relationship, not easy to leave...

What is EASY?? NOTHING is meant to be easy. But because of her children, she MUST leave. If...IF her husband values their relationship, he would not have done such things. I KNOW it is hard when so much affection and emotion was put into the relationship. I HAD ended a 4 year relationship, it was not easy, but I KNOW it was the best decision I MADE.

*having headache now, MUST SLEEP!!! anyway, this is a true story told from a friend of a friend of a friend of a friend of...so, there is no point figuring who it is...sorry if there is any grammar/spelling mistakes...*

So, what do you think??