Why do women moves on extremely fast in their new relationships?

04/08/XX she dumps her previous relationship and then enters a new relationship, then she changes her last name to her new partners last name on the same day

04/12/XX she gets engaged đź’Ť from her new boyfriend and announces her engaged to everybody

04/14/XX, she announces her pregnancy

Etc and etc
Why do women moves on extremely fast in their new relationships?
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