31 YEARS OLD

The woman, she had a boyfriend who was 42 years old, lived together with his 2 daughters from this August. Her boyfriend and his daughters took a bath when she exploded and said like that "Why do not you join me!". And her boyfriend said "Get out here, I'll be exploded in anger" And then, she wanted to kill his daughters when they took out a bath. When she cut them, his daughter said "Sorry Emi-chan". Emi is the woman's name. His daughter survived by her boyfriend, but...
I'm 31 years old, woman. And suspect person, her age is the same with me. But I can't understand why she wanted to kill them. Probably she had jealousy. That's all, I guess. But why she wanted to kill... it's miserable. I know what is jealousy, but in this case, it's really stupid. And his daughter said "sorry", but she is 8 years old. 8 and 31... Sheakespear said "Love is blind", I think so. But in this case, really stupid. And I pity his daughters.