You were clearly WAY too attached and invested. Your heart can only be broken if you let it. Focus on other stuff and be in control of your relationship next time.

I texted her saying how could you do this to me, etc and she said he was just a friend. She swore to my face during the break up that no one else was in the picture.

First of all, major frame loss. Dries her up like the sahara desert. Second of all, in her mind she swore there wasn't anyone else just to try and protect your feelings.

During the trip I'm texting her saying how much I care about her and how I want to build a life with her, have kids, marriage, etc.

Unless you're fucking Brad Pitt this shit will only have a terrible effect on your relationship. You can be vocal about your feelings but don't act like an entire boysband crying about getting old together... It scares her away, you're both young, you should live day to day, year to year, not plan your entire existence already. The mystery is gone and so is all attraction. You were clearly not willing to walk away EVER, even if she lost respect for you or didn't treat you like you deserve.

She tells me she wants to break up and I'm crying my heart out and begging to make this work. Literally for hours. Saturday morning we wake up and I continue trying to keep the relationship together, but she's adamant and says no and she's sorry. We pack all her stuff up and move it to her moms house. I was fucking crushed. I was over at her mom's until midnight just talking and pleading for us to work this out and I'd do literally anything to make it work.

Major oneitis. Get your shit together and don't get too attached to anyone unless you happen to make things work in your relationship year after year without much effort. Those are the only people that get old together. Lift, read the sidebar and don't fucking make the rest of your life someone else's responsibility like you tried with this chick. If anyone's responsible for the happiness of both you and your partner, it should be YOU.