Also, as for the Gabby / Santiago connection, there's also this photo:
View attachment 3369523
Which sheds light on their relationship a lot more, Santiago seems to be Gabby's coach or scout or something related to her running days... the other picture when they're in a tuxedo and dress might very well be from a celebration when she won a race or something, which would be a VERY important event in Gabby's life (warranting a big ass picture in her home), and since he's her coach or something like that, it makes sense he would be in the photo.
Anyhoo, it seems Gabby has always had a crush on him, despite being married, and that's why she's also crushing on the MC... it's even hinted in her conversation with Ximena.