'Caitie' is a reference to what Amunet calls Caitlin in season 4 of Flash. 

...

Lisa had stopped being apart of ColdFlash. After all, she had slept with Barry. There was no redemption for her.

So that's why she decided to go to STAR Labs and admit it and hope Cisco didn't breakup with her. (She was coming to admit she cheated on him with his best friend, then broke his already shattered heart)

God, she seriously wished she hadn't done that.

So, when she walked in to STAR Labs, she was extremely nervous. She looked around for Cisco, (She wanted to tell him first) but she didn't see him. She did, however, notice Caitlin on the computer. She padded over silently, and looked over her shoulder to see something titled, Diary. Caitlin had a diary?

"Hey, Sweetie," Lisa said as she successfully hid giggles from her comrade. But Caitlin's reaction was priceless.

She jumped up with ice in her hand, (How did she turn around in midair?) facing Lisa. As soon as she saw that it was Lisa, her eyes turned back to brown. (When did her eyes change color? Not to mention the ice in hand...) 

"What's with the ice?" Lisa asked. Caitlin looked shocked. She looked from her hand to Lisa and back. Suddenly, the ice disappeared.

"What are you doing here, Lisa? And, why did you stop coming?" Caitlin asked. "Did we do something? Did Cisco do something? Did I do something?" Lisa looked at her feet. They were a lot more interesting than usual. 

"Look, you did do anything. Cisco didn't either. I did. I couldn't face you guys, nor risk seeing Barry, so I just quit. I shouldn't have, but I did, and for that I'm sorry." Caitlin's face went from sad to angry in seconds.

"Do you know what you did to Cisco? Did you even think before you stopped seeing your boyfriend enough to make someone think you were breaking up with them!?!?!?!" Caitlin yelled. 

Lisa shrank away. To be honest, Caitlin was exactly right. She hadn't been thinking about Cisco and his feelings.

"You're right, Caitie. I didn't think about Cisco, or you, or anyone but myself. That's the problem. I did something, and because of it, I don't know what to do, so instead of asking for help, I pushed everyone away because I knew how you'd react. I'm sorry, and I really, really, don't deserve to be forgiven," Lisa said sadly. 

"I should go," she said as she walked to the door. 

"Wait!" Caitlin said as she ran toward her. "It's not me who needs to forgive you; it's Cisco. And he deserves to hear a reason why his girlfriend hasn't seen him in two weeks or more; I lost count."

Lisa turned to her with tears in her eyes. "But I don't deserve to be forgiven."

"That's not you decision to make," Cisco said as he walked into the room. Lisa gasped. It really had been awhile since she'd seen him.

She felt tears roll down her cheeks. It really had been awhile since she'd seen him. She had missed him so much the whole time she hadn't visited him.

"I'm so sorry!!!!" she yelled as she flung herself into his arms. He flew backwards with a yelp. "Don't tackle me!!" he said from the floor.

She giggled. That was she had missed most. Lenny never, ever laughed/smiled. Neither did Mick,   although she couldn't blame either of them.

"I missed you so much, Lisa. Why did you leave?" Cisco asked.

Lisa gulped. It was time. 

"Because I slept with your best friend," she said, as she once again looked at her shoes. She heard a gasp come from Caitlin, and she could have sworn she felt Cisco eyes on her. "You what?" he asked in shock. She blinked back tears. She knew she could have forgiven Cisco, but that was only because he was the only bright thing in her dark world. 

She couldn't imagine her dark world without a little brightness.

She looked up to see tears in Cisco's eyes as she answered. She owed him that. "I slept with Barry. But I didn't do it on purpose. And neither did he," she said as she knew where Cisco's thoughts might lead. "He was drunk, and I didn't know what Barry looked like. He had just been hurt pretty bad and I only made it worse. 

When he woke up and I realized who he was, I made the mistake of yelling at him to get out. I didn't stop, not until I saw the tears in his eyes. He looked me right in the eye and said, "Guess all Snart's are the same," then he proceeded to tell me, and I quote, "Well, seeing as how your brother had a one-night-stand with me, and was rude to me too. The only difference? He left a note explaining that I was just some hookup, didn't mean anything, he didn't care about me, hope doesn't make fights awkward instead of yelling at me. Not to mention he didn't take advantage of me or my feelings. Oh, wait, he did. Just 'cause he got rejected. So, yeah, thanks for a repeat. Really needed it."

I remember that really well.  He looked so lost, so hurt, and I caused that. I caused that! I caused someone's broken heart! And I thought, no, knew, if I told you, then I would have caused another one. And I couldn't just keep this from you if I saw you everyday, so I stopped coming. I treated this situation wrong, and I'm sorry."

Cisco turned away from her. "Do you actually feel bad?" Lisa nodded. "I do. I should never have slept with your best friend, treated him like that, and lied to you, not to mention making you think that I was leaving you." Cisco shook his head. 

"Wow. I can't believe you! You forgot one tiny apology. It doesn't matter that you slept with Barry; it matters that you slept with anyone! How could you!?!? You don't even feel bad about sleeping with some other guy! You only feel bad because it was Barry and it might have ruined your brother's happiness! You don't care about my happiness!" Cisco screamed at her.

Lisa felt tears fall for the first time since she had run away with her brother. It was a painful memory, so she always tried not to think about it. So she saved it for later; Cisco was her priority right now.

She tried to think of something to say. The silence was making her go crazy. 

Finally, Cisco broke the silence. "Get out," he said calmly. 

"No," she said. "We need to talk about this." Cisco looked at her like she was a stranger. "What is there to talk about? You cheated on me, and you aren't sorry. Not to mention that it was with my best friend. So, get out before I lose my temper."

So, she swallowed her pride and got on her knees. "Please, Cisco. I need you to forgive me. Please. You're the only bright thing in my life. I can't live without you."

Cisco looked at her and snorted. "I don't believe you. I can't believe I went out with a criminal."

She felt her heart shatter completely. She couldn't stay anymore.

"Well, if that's how you feel," she said as she tried desperately to hide the tears. She ran out, feeling like her heart would never be whole again.

Note: Sorry for the lack of ColdFlash in that chapter. This chapter was very hard to write because it kinda got away from me. I planned to have Caitlin have more of a say, and to make Cisco a lot nicer. Seriously, he was understandably upset, I had just planned to make Cisco nicer. Also, now you're on two different paths: ColdFlash and GoldenVibe. Let me know who you like more in the comments!!!