It was a deep prayer and revelation born of the understanding that the Holy Spirit (who overshadowed her) revealed to her in a deeply spiritual way. The only way that all generations will call her blessed would be if it was the will of God and that He revealed that to Mary through the Holy Spirit.
I don’t think I’m making myself clear...
Mary said - correctly - that all future generations would call her blessed. Yet she never so called herself!
Stating what you believe others will call you does not mean you agree with their beliefs.
Please tell me where Mary calls herself blessed, or where Jesus calls her blessed. We have Mary saying others will consider her blessed, but that’s it.