Ernest Hemingway's short story "Hills Like White Elephants" was published in 1927, and to some degree her indecision reflects the cultural attitudes of the period.
In the story, Jig and a man who is not named sit in a railway station and talk as they are waiting for a train to arrive. It is gradually revealed over the course of their conversation that she is going to have an operation, and then it is revealed that the operation is an abortion.
As abortion was even more controversial (and scandalous) in 1927 than now; it representes a huge decision for the couple and especially for Jig. While the man is claiming that the decision is Jig's, it is obvious that he would prefer her to have the abortion. She is not entirely sure if she wants the abortion; she might actually prefer to settle down and get married and have a family rather than living the life of a Bohemian traveling around Europe and partying with no real goals. Her pregnancy is causing her to reflect on the meaninglessness of their current lifestyle. The problem she encounters is that the pregnancy has changed her and their relationship, and that even when she tries to carry on as in the past, it doesn't really work:
"You started it," the girl said. "I was being amused. I was having a fine time."
"Well, let's try and have a fine time."
"All right. I was trying. I said the mountains looked like white elephants. Wasn't that bright?"
"That was bright."
"I wanted to try this new drink. That's all we do, isn't it - look at things and try new drinks?"
"I guess so."
Overall, the reason for her indecisiveness is that the choice to have an abortion is a difficult one, and she is ambivalent not only about the choice of having the abortion but the way that choice has made her reflect on the superficiality and meaninglessness of her current lifestyle.