Adam Rose/FOX Break out the champagne (or apple cider for all you fans under 21), Gleeks—it’s time to celebrate!Glee’s graduation day is finally upon us as Rachel (Lea Michele), Finn (Cory Monteith), Kurt (Chris Colfer), Santana (Naya Rivera) & Co. are finally saying goodbye to McKinley High after three seasons of singing, solos and slushies. Grammy winner Gloria Estefan makes her long-awaited debut during tonight’s finale as Santana’s mother, and we chatted with the legendary singer about their relationship and “emotional one-on-one scene,” why she decided to guest star and more! Plus, why isn’t she singing on the show?! MORE: Spoiler Chat Daily: White Collar Fist Fight! Plus, Scoop on Smash, Glee and More! Gloria tells us she and her daughter are big fans of the show and first went to the set about a year and a half ago, where she met Naya, whom she calls super sweet,” for the first time. Later, “[Ryan Murphy” called to ask if I would be interested in playing her mom, and I was like, ‘Yes, are you kidding me?!” she recalls, “Especially after meeting that mean grandmother. That was not nice.”Of course, Gloria is speaking of Santana’s grandmother, who heartbreakingly rejected her granddaughter after she came out to her, going so far as to kick her out of the house. Don’t worry, fans, Mama Lopez is nothing like Grandmother Lopez—Gloria describes the two women as “very different…Her mom is going to want to be there for her and be supportive.”So just what is Mirabel Lopez like? “Snarky like Santana and sarcastic because the apple can’t fall that far from the tree! She wants her daughter to be happy because she wasn’t,” Gloria explains. “She wanted to sing and, probably when she got pregnant with Santana and her husband was going to med school, she got a job to help him through med school and focused on Santana. Her mom probably told her, ‘You can’t have that music career now, you have a baby.’ Her mom looks like a tough cookie!”So what does Gloria hope fans take away from Santana and Mirabel’s relationship? ”I hope particularly for the gay fans, because she’s got a lot of them, she plays a gay character, I want them to know that despite the fact that people might respond in a bad way or in a way that’s not supportive in their life, even someone as close as a grandma, that there are parents that can be very supportive,” she says. “For the parents, I think it would be a good thing to see. It addresses an issue that is important.” MORE: House Series Finale: Did House Get a Happy Ending? While Gloria wasn’t on set for the final days of shooting, she tells us Mirabel and Santana share an “emotional” but still “very in-character” scene about Santana’s post-McKinley High future. ”It was great. We clicked,” she says of working with Naya. “We just fell into that role very easily. I’m very maternal and she’s a fan, from what she told me back in the day. She’s very sweet, she’s a good actor. It was fun to play.”Gloria tells us most of her screentime will be shared with Naya and Heather Morris as Mirabel, Santana and Brittany, whom Gloria says Mirabel has met before, have a bit of “a girls night” at Breadstix, which she describes as a lot of fun, until “Santana drops a bombshell that shocks everyone at the table.” While she wouldn’t divulge much about the jaw-dropping news, she would say “it’s funny.” Hm…shocking and funny? Sounds like Glee to us!Though Gloria’s fans will be sad to learn that she is not performing in the episode, there is one person who is excited by her lack of singing: Gloria! She tells us that singing on the show would make viewers think of Gloria Estefan instead of Mirabel Lopez, which isn’t what she wanted for her appearance on the show. “They can see me sing anywhere else anytime! That’s what I do!” she says with a laugh. Glee’s finale airs tonight at 9 p.m. on Fox. PHOTOS: Glee Super Gallery: The Best Photo and Quotes!