while she and Lincoln were courting, she seems to have been a charming young woman - perhaps a little more willing to debate politically than might have been seen fit for a woman of her breeding, but charming nonetheless. Her major break seems to have occurred at the death of their son. She was famously very ostentatious in her displays of grief. Finally Lincoln brought her to the front room, which faced a mental health asylum across the river, and said to her (paraphrasing), "See that? If you continue on as you have, I shall be forced to send you there." She understood the threat and became more demure in her grief.

Still, she was regularly a difficult woman to work with, both for herself and for her husband. By this I mean MTL often provided Lincoln with advise about his appointments and seems to have had some influence. She felt as his wife, she should have some definitive say in his appointments, and often grew upset when he ignored her advice.

After the death of Lincoln, she wholly embraced the role of a mourning widow, and she believed Congress should support her financially because her husband had given his life for the cause of Liberty. However, MTL was a known spender and could not seem to live within her means. With the help of her dressmaker, Elizabeth Keckley, she devised a plan to sell some of her old clothes to raise funds. It really was a scheme, and she relied on unscrupulous men who basically cheated her as much as they could. She continued to ask Congress for increases in her allowances over the years, complaining that she could not live on such money.

I understand this provides only a cursory glance at MTL and her behaviors. For more information, I recommend the following sources:

Mrs. Lincoln: A Life - Catherine Clinton

Behind the Scenes - Elizabeth Keckley (note: this is Keckley's autobioaphy, but once MTL enters the scenes, she remains; also the edition I had included letters sent from MTL herself, which should give you an idea of the sort of woman she was)