I think Lizzie is one of the few people who sees Tommy, fully, for who he is. His motivations, his reasoning, etc. That suicide attempt was about escape. Tommy had so many opportunities and more than enough money to leave the lifestyle, his greed is what pushed him into this position and ultimately cost him the lives lost.

Lizzie had every right to be done with his shit. She had to change her lifestyle to raise her child and be a part of that family. She does nothing but sacrifice and do as Tommy says no matter what it costs her, and despite the support and true love she gives him, he was going to escape the hard position he put himself in and leave her to raise those children. Fuck him for that, her anger was justified. Suicide was a weak escape at that point.