Judging from Curley's wife's flirtatious behavior with the other men on the ranch, she is not in love with her husband or with anybody else. When she has a long talk with Lennie in the barn before he accidentally kills her, she reveals a great deal about herself. Even when she was fifteen years old she wanted to get away from her home because she felt it was too confining. The only way she could think of escaping from home was by meeting a man who would take her away. She made at least two attempts to do so but was thwarted both of those times by her mother. She tells Lennie:
"Well, I wasn't gonna stay no place where I couldn't get nowhere or make something of myself, an' where they stole your letters...So I married Curley. Met him out to the Riverside Dance Palace that same night."
That was the night she had an argument with her mother. The implication is that she married Curley because she was angry at her mother and determined to get away as soon as possible. She is a very young girl, probably only about sixteen, although Steinbeck doesn't give her exact age. Several men, including George, refer to her as "jail bait." That was a term applied to a promiscuous underage girl who could get a man jailed for statutory rape if she was "under the age of consent." At that time the age of consent in California was eighteen.
She makes it clear that she does not love Curley (which should come as no surprise considering his character and personality):
"Well, I ain't told this to nobody before. Maybe I ought'n to. I don' likeCurley. He ain't a nice fella." And because she had confided in him,she moved closer to Lennie and sat beside him.
Moving closer to Lennie is a bad mistake, and it will lead inevitably to her death as well as to Lennie's.