"You taught me to be strong," she could be seen telling her cousin in videos posted by fans, going on to call Priscilla "brave" and "beautiful."
Sending the couple her love, she added, "I pray for you guys all the time."
"I wouldn't want anyone else standing next to me at the altar," she wrote alongside a slideshow of photos taken from the trip, including a photo of herself and Gomez laughing on the beach. "My maid of honor really showed out this weekend and threw me the bachelorette party of my dreams. I am forever grateful."
While shopping for dresses together in December 2017, DeLeon shared an adorable clip of the cousins posing with an "I Said Yes to the Dress" sign.
"When your maid of honor makes your dream dress a reality and surprises you with it!" she wrote.
Gomez, who is also godmother to her cousin's son, was even on hand when her cousin first got engaged in March 2016.