Why does my ex girlfriend/friend block me every time she gets into a new relationship?

So my ex-girlfriend is always broking me every time she gets into a new relationship. She will block me for months, but as soon as the new relationship fails or she goes to mental health issues, she will text me for support or for help then block me agin after meeting a nre guy. I have gotten very hurt from this she was a childhood friend, and she said sorry recently for doing it but then it agin. Said she did it this time to focus on her new boyfriend after promising she wouldn't do It agin. This has been going on for about 5 years now and I known her for 15 years.
Why does my ex girlfriend/friend block me every time she gets into a new relationship?
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