Sorry to hear about your heart break. Heartbreak really sucks, and leaves you questioning a lot of things from the past (why is she sad, why are you sad, who should you trust, was it the right decision etc.). Long Distance Relationships are really hard to maintain, but the both of you have done your best to maintain the relationship. I can't say whether the choice that you've made is right or not, or who's lying and what not. But all I know is it was a really difficult decision that you had to make.
I feel, in a break up situation, no matter who's the dumper or dumpee, both parties will still go through the same grief and sadness from the break up. Because it's hard to detach emotions and feelings from memories when you were together. It's normal to be missing your ex, especially at the start of your break up. A person whom you once spoke to frequently, suddenly gets cut out from your life, and it's an awkward feeling to have, with a sense of loneliness. Even though she may have someone else to go to for comfort, a break up still hurts for both parties.
Try and fill your time with as much activities that makes you happy, or chat with friends. Even better if you can find someone who you can speak to in a safe space without any judgement (like a counsellor, or therapist). Crying helps a lot with processing grief, don't hold back on your emotions and allow yourself to feel the emotions that comes from the breakup.
If it's alright for me to ask, when she admitted that she was giving up on you, and told you that she wanted it over, did she explain what the reason was?
Happy to listen to you more Ryan2021, please take care of yourself first.