She started seeing someone like not even a week after breaking up with me

So I (21)m found out and my heart and mind is racing. I was seeing her (19)f. For three months everything was good we were actively pursuing each other and it felt like something really real. Long story short she messages me by text after new years that we are not working out. I lost my self and spiraled sending messages like ok I had fun while lasted, then switching up and sending and trying to meet her in person to talk. She was not texting me and waited till even the end of the day and sometimes not at all. I couldn’t believe it. I even went so far and sent a closure text saying how I enjoyed the time we had and I didn’t want to change her mind. I started to feel better. But then I ran into her today we exchanged a few words and then this guy pulls up in his car honks and she looks at me and says she has to go. I don’t even know what to think. I don’t want to assume right away but it makes so much more sense exposing her silence. I’m upset and hurt and I feel like my trust and honesty is worthless. I went to hell and back for her but she just drops me like that.