That's sussy, Ichika
After looking at the hints made in regards to the bride, all four hints have some sort of involvement with Nino:
Hint #1 is obvious with Nino being one of the five Quintuplets.
Hint #2 brings us back to when Nino had Fuutarou's Student Handbook where she asked Fuutarou to pierce her ears. This part of the manga could be simply put there to have some motive for Nino to find out what was in the handbook, but it's possible that it relates to the hint as well.
Hint #3 I believe was shown to be stated that all five Quintuplets were holding Fuutarou's hand.
Hint #4 is related to Nino as she had previously planned to kiss Fuutarou. I'm not exactly too sure if this was in chronological order, so I might be wrong. However, if what I stated about Hint #4 was correct, I think that Nino might be the bride after all.