This happened to two of my friends that purchased an apartment together in Recoleta many years ago. One loved it and one wanted to sell it. The situation was tense. That situation was different as they both put in 50% of the funds to buy the property and furniture. I am not sure if your girlfriend
@fool in love is contributing anything but in my friends situation they did not have anything agreed ahead of time.
The value went up drastically and one wanted to sell and one did not. The one that did not want to sell did not want to pay an inflated price for the other 50% and the one that wanted to sell wanted 50% of the increased value. After seeing that I would recommend that you have all the various scenarios worked out how you might handle that.
Or reading from your other post, it seems like your relationship is new. Maybe just buy the apartment and put it under your name and let her live there free and see how the relationship goes. I wouldn't rush into an apartment purchase on a new relationship. But that is just me.