Why do women move on so quick?

I was told we’d be back together in 6 months when she works on herself. Promised not to see anyone.

Last week (45 days) in and she’s already seeing someone and texted me telling me to move on. Now she’s saying she felt the breakup was long overdue.

None of this makes sense to me. I changed, did better and she said she just needs some time to see it etc. like at least keep your word. I feel so let down. And I’ve tried to move on but I still think about her and even have dreams of us together. I’ve accepted the fact I don’t want her back and it’s disrespectful to be used and option B. Fuck my heart.

She was my first love for 5 years and long distance in NY and CA.