Very class conscious and superficial, Daisy's character seems incapable of true feeling that would alter her actions if she were in the modern world. For, there are yet the "sorority sisters" of contemporary life who act according to the dictates of their elite group and place any substantial and true feelings that they might feel burgeoning in them as secondary to the goal of marrying a rich man and having a position in upper-class society. Remember that Nick remarks that she has a voice that "sounded like money" and "a deathless soul."
Had Daisy had more integrity, as #6 suggests, she would have made different choices, regardless of what era she existed. Human foibles don't change over time; the study of history is where you see the same types of people making the same poor choices over and over.
I think we might need to answer the question "Does Daisy have any integrity?" before we can tell what she would choose to do in today's world.
Has Daisy left behind all her ideals/values and chosen a path where she will be identified only by wealth and possessions? Or is she actually still pursuing the love she lost upon entering adulthood?
If we see her as possessing some integrity, we might imagine her going her own way in today's world and eschewing the relationships that compromise her identity. If we see her as having abandoned her values in the pursuit of material wealth then it seems like we'd have to imagine her in material pursuit in today's world.
Daisy's choice of Tom over Gatsby is partly dictated by her position as a woman in the society of her era -- an era in which women had much less power and independence than they have today. Divorce was also much more frowned upon in that era than tends to be the case today. In addition, "no-fault" divorce rules that exist today might make it possible for Daisy to divorce Tom and still share a great deal of his estate. All these factors might make Daisy more likely to divorce Tom today than during Fitzgerald's day.
I'm not so sure her choice would have been different today. Knowing Daisy's personality, I think she seems more likely to settle for the person who can provide for her and make her comfortable. This person is Tom. I think Daisy would have the same personality now, so she would be less likely to go with the man who would be more of a risk (Gatsby), and instead stay with Tom. Yes, today we have different values as far as money and happiness go, but I don't think that would change the circumstances much for Daisy.
For one thing, Daisy might have shown interest in Gatsby in the first place. She met Gatsby before she was married but could not marry him because of his social standing. In today's world, this is much less of an issue. People are not prevented from dating or marrying because of social class, race, and other discriminatory factors nearly as often as they once were. This is not to say that it never happens in the modern world, but it is certainly less prevalent today than it was during the roaring 20s.
Obviously, the final answer is that we have no way of knowing how Daisy's choice of husband might be different if it were happening today instead of during the 1920's, the time period of The Great Gatsby. There are too many variables that come into play with such a decision to reach anything beyond reasoned guesses.
According to Jordan Baker, Daisy was infatuated with a soldier who she met before he went overseas to the war, but her family prevented her from continuing the relationship. Daisy moved on to marry the very wealthy Tom Buchanan, although she seemed to have second thoughts while heavily drinking by herself shortly before the rehearsal dinner.
Here, deares'." She groped around in a waste-basket she had with her on the bed and pulled out the string of pearls. "Take 'em downstairs and give 'em back to whoever they belong to. Tell 'em all Daisy's change' her mine. Say: 'Daisy's change' her mine!'
Daisy did go through with the wedding, but never forgot her fascination with her first love, the soldier who reinvented himself as Jay Gatsby.
In today's culture, the parents of most young women would not be able to control their movements and contacts to the extent that Daisy's parents did. If she had been able to travel to New York to visit her soldier before he left for Europe, that may have led to a wedding. However, Daisy truly loved being rich and may have concluded that a soldier's pay would not sustain the lifestyle to which she had been accustomed since childhood.
I think Daisy does have very different choices today. Unless she signed a prenup she would do well in a divorce since Tom was openly having an affair. She is from old money herself so I don't know that she would lose social standing by divorcing Tom today. She may by marrying Gatsby though since his wealth is questionably obtained. Is she motivated by love, money or prestige?
Tom's violence does complicate the situation though. He broke Myrtle's nose when she angered him. I wonder if Daisy hasn't experience Tom's abuse. Would that keep her from leaving him? Did it effect her decision at the time?