In Qin Xue's eyes, her friend's behavior was utterly foolish. If she had used that money to invest in herself, Qin Xue believed she would be happier, and perhaps she might even have the charm to attract better people.
Any decent man would be a step up from her husband, surely. Even if she didn't want to divorce her scum of a husband, wouldn't he change his ways if he saw such a transformation in his wife? He wouldn't have time to go after other women, right?
The main reason for such issues in a marriage is often that the spark has worn off over time. Love slowly transforms into family affection, and once the novelty is gone, problems begin to arise.
To put it simply, after marriage, a woman revolves around her family. Her thoughts are concentrated on her husband, her children, and her in-laws, leaving no time for herself. She stops focusing on her appearance, which used to be so important.