Divorce vs annulment.
So then, if your aunt wants to remarry now, is she just SOL or what?
Nope. She just can't get married in a Catholic church with a Catholic service. She can still get a marriage license and get married anywhere else by anyone else who's licensed to marry people.
Given the bull**** the Catholic Church regularly puts non-Catholics through when a Catholic plans to marry one, a lot of Catholics don't even get married in their Church anymore. My parents (Dad - Irish Catholic; Mom - Irish Protestant) ended up get married in a Protestant Church; not because mom has anything against the Catholic Church specifically, but more because it was going to be an absolute pain in the ass.
Traditions like this is why the Catholic Church is bleeding membership to evangelical churches the world over. They're sending themselves into irrelevance at an unprecedented pace.
I know there's this historical argument that the Church has been around for 1500ish years and that's because of tradition, but most students of history will tell you that has far more to do with the isolation of certain pockets of populations, lack of widespread education (which the Church actually controlled), the Church's control over knowledge in general pre-Enlightenment, and their direct role in the everyday lives of most of humanity. Globalization, widespread public secular education, and the emergence of science as a discipline and rationalism generally have vastly undermined the Church's control over people's everyday lives. Really, the only reason the Church remained as strong as it did through the Medieval period was their suppression of science and jealously-guarded control over knowledge. The Enlightenment changed all that, and the Church has been in a downward spiral toward niche irrelevance ever since. By far the majority of today's Catholics do not strictly follow Church teachings; they pick and choose what works for them.
Looking even at the erosion in the last 150 years, unless the Church is willing to change I think they're going to push the Church further out of the daily lives of its followers. I know they think that they can stay the course and society will change, but there's a fundamental flaw with that reasoning - science is removing people's need to use faith to interpret the world around them. There will always be a role for religion, I suspect, but it's not the role the Church leadership wants it to have. In short, unless they begin a process of realignment of Church teachings with the way people learn and know about their world today, they're pushing themselves into a decline it won't recover from.
Islam will eventually go the same way. Religious influence over daily life diminishes as a population increases their education and, consequently, their standard of living. When people lose the widespread, generalized fear of early and meaningless death, religion tends to lose its grip on them. Let's face it - the only two real forced holds religion has on people is a monopoly over general knowledge and education, and a monopoly over spiritual life after death. When they lose grip on education/knowledge, people gain knowledge of the world around them. While that spiritual life role can still exist, it's a lot harder to motivate the same levels of fear in spirituality that you otherwise can when the people you are preaching to are as educated and capable of sharing ideas as you are.