My (25M) girlfriend (24F) wants to break up cause I got 4/10 on "happiest I've ever been" scale. Is she actually serious?

Once a week me and my gf play "happiest I've ever been" game. It's a simple game that goes like this:<br><br>Person 1 asks person 2 "On a scale from 1 to 10, where 10 is the happiest you've ever been, where are you right now?". Then, person 2 gives an answer from 1 to 10, and person 1 does the same thing.<br><br>It's a fun little game, pretty random too.<br><br>But today, as soon as person 1 (me) asked person 2 (gf) the question and she gave answer 4, I felt like something was off, so I asked "wait, what's going on? You're not even at 5?" and she said "yeah, we're gonna break up" and I said "WHAT??? WHAT'S GOING ON???? WE WERE IN LOVE?????? HOW CAN THIS HAPPEN?????" and she said "I'm sorry, but I think we've grown apart. I've been feeling unhappy with our relationship for a long time now, but I didn't want to break up with you until you find someone better. You're a great boyfriend and an even better person. I hope you find someone who's even better than me" and I said "well, I guess it's over then. I'll always love you" and she said "I'll always love you too" and I said "that's not what I meant" and we both cried and held each other tight.<br><br>So, yeah. That's pretty much what happened. She wants to break up, and I don't really know what to do about it. Does anyone have any advice for me? How do I get her to stay with me?