Quinn really can't believe she let herself break down in front of Brittany and Santana. She yelled and screamed and then sat on a bed and cried before letting herself be talked into getting half of her hacked off. She remembers Santana's head resting on her shoulder and Brittany toying with her hair and suddenly feels a little less pathetic about the whole thing. She hates to admit it, but she really misses the Cheerio trio friendship. They're little moment after her mild mental breakdown makes her remember how good it felt to know someone was on your side.
She goes back in her head to when it all fell apart between her, Brittany, and Santana. She remembers a hot summer day, her and Santana sitting in patio chairs on the Lopez family porch. Two ice cold strawberry lemonades sat on a nearby title, little drips of water sliding down the glasses. Santana made a comment about how she wished Brittany was there with them, but that there was a perk to it just being the two of them. Before Quinn could ask what the perk was, Santana leans forward and gently presses her lips to Quinn's. She tasted like cherry lip gloss and strawberry lemonade.
Quinn remembers how nice she tried to be in her rejection and how gently she let Santana down, but she also remembers how their friendship deteriorated into something awful. Santana couldn't stand the fact that her friend that she was crushing on knew she liked girls, but mostly that Quinn liked the kiss but turned her down because of the bible. Soon, the two started sabotaging the other, and the rest was history.
That was Quinn's first kiss. Santana kissed her and while lips-on-lips felt exciting, she didn't feel like she could continue it. The second person Quinn ever kissed was Finn, and then came Puck on a drunken night full of new feelings. Sex felt so good in a way that made her feel uncomfortable. She really wasn't emotionally prepared for that kind of intimacy. One of things that Quinn really liked about Sam was that he didn't really push her towards a physically mature relationship after she took his promise ring. She'll always hate herself for cheating on him and ruining their love. The one relationship she actually likes was the one she casually threw away. (She was sober that time)
They try to keep it a secret, but Quinn figures out pretty easily that Mercedes and Sam are a couple. The first thought that comes to mind after Kurt spills the "happy news" is to walk right up to Sam and kiss him and beg for him to find some feelings he might still have for her deep down. She knows she's a cheater and liar but she'd give anything to be his love again. He always made her feel beautiful.
Despite her pain she finds room to be happy for Mercedes and Sam. Someone's finally been smart enough to like and date Mercedes and Sam has a girlfriend who will surely be faithful. Quinn hopes she hasn't left any scars, and that Sam will know he can trust his new girlfriend. All Quinn can do is hope. Still, she feels a little bit special when she realizes that there are no promises or promise rings involved in this new relationship. Quinn will always be his first. (And at the same time, probably his worst)
Quinn walks into glee club and sees Santana and Brittany holding pinkies and looking at each other lovingly. She sees Finn and Rachel rubbing there noses together and being completely and utterly in love. She sees Puck and Lauren making out. She even catches a few "secret" glances between Sam and Mercedes. In the time it had taken her to mature past her insecurities and to come of age, she had lost every chance at love.