Courtney Mazza, Mario Lopez, and Eva Longoria on March 18, 2011 in Las Vegas, Nevada. Credit: Denise Truscello/WireImage

Her best friend's wedding!

Eva Longoria was on hand to celebrate longtime (and strictly platonic!) pal Mario Lopez as he exchanged vows with love Courtney Mazza December 1 -- and she says she's thrilled about the pair's decision to tie the knot.

"I couldn't be happier for them," the Desperate Housewives alum, 37, gushed to Us Weekly after attending the lavish ceremony, which took place at Joe Francis' home in Punta Mita, Mexico. (Longoria held tight to the couple's tot and flowergirl, 2-year-old Gia, during the celebration.)

The Extra correspondent, 39, and his girlfriend of four years said "I do" in front of 200 guests -- including Longoria -- and then proceeded to party the night away, grooving to old-school hits like "Ring My Bell." (At the end of the bash, the newlyweds jumped into the pool!)

Pre-ceremony, Lopez said he had no idea making it official with Mazza, 31, would be such a moving experience.

Admitted the X Factor host, "I didn't think I'd get emotional, but I did!"